Gingival blood flow in periodontitis patients before and after periodontal surgery assessed in smokers and non-smokers

BACKGROUND

The aim of this study was to evaluate the gingival blood flow of smokers and non-smokers with periodontal disease before and after surgical periodontal treatment.

METHODS

Nine smokers and six non-smokers with at least two periodontal lesions were included in the study. Laser Doppler flowmetry was used to measure blood flow in two gingival sites and two skin sites. Two intrabony defects were treated surgically at the same time; enamel matrix derivative was applied at random to one of the sites, whereas the other site received a placebo gel. We measured resting gingival blood flow (GBF) and responses to cold pressor test (CPT) and to smoking and made continuous measurements of blood pressure (BP). Resting GBF levels of 26 young healthy subjects were used as a reference value.

RESULTS

Resting GBF was significantly lower for the periodontitis patients compared to the reference subjects, regardless of smoking habits. GBF and gingival vascular conductance (VC) decreased significantly pre- and postoperatively in response to smoking. CPT evoked significant decreases in VC in smokers and non-smokers. Skin blood flow decreased significantly in response to CPT, more so in the non-smokers. BP was significantly higher in the non-smokers.

CONCLUSIONS

Resting GBF of periodontitis patients was not lower in smokers than in non-smokers, but it was significantly lower than in the younger reference subjects. In contrast to our earlier findings in healthy subjects, smoking one cigarette may cause a decrease in GBF and VC in periodontitis patients. These observations suggested the existence of a dysfunction in the gingival vasculature in smokers and non-smokers with periodontitis.

Adrenergic control of venous capacitance during moderate hypoxia in the rainbow trout (Oncorhynchus mykiss): role of neural and circulating catecholamines

Central venous blood pressure (P(ven)) increases in response to hypoxia in rainbow trout (Oncorhynchus mykiss), but details on the control mechanisms of the venous vasculature during hypoxia have not been studied in fish. Basic cardiovascular variables including P(ven), dorsal aortic blood pressure, cardiac output, and heart rate were monitored in vivo during normoxia and moderate hypoxia (P(W)O(2) = approximately 9 kPa), where P(W)O(2) is water oxygen partial pressure. Venous capacitance curves for normoxia and hypoxia were constructed at 80-100, 90-110, and 100-120% of total blood volume by transiently (8 s) occluding the ventral aorta and measure P(ven) during circulatory arrest to estimate the mean circulatory filling pressure (MCFP). This allowed for estimates of hypoxia-induced changes in unstressed blood volume (USBV) and venous compliance. MCFP increased due to a decreased USBV at all blood volumes during hypoxia. These venous responses were blocked by alpha-adrenoceptor blockade with prazosin (1 mg/kg body mass). MCFP still increased during hypoxia after pretreatment with the adrenergic nerve-blocking agent bretylium (10 mg/kg body mass), but the decrease in USBV only persisted at 80-100% blood volume, whereas vascular capacitance decreased significantly at 90-110% blood volume. In all treatments, hypoxia typically reduced heart rate while cardiac output was maintained through a compensatory increase in stroke volume. Despite the markedly reduced response in venous capacitance after adrenergic blockade, P(ven) always increased in response to hypoxia. This study reveals that venous capacitance in rainbow trout is actively modulated in response to hypoxia by an alpha-adrenergic mechanism with both humoral and neural components.

Enhanced sympathetic reactivity associates with insulin resistance in the young Zucker rat

Somatosympathetic reflexes were studied in young hyperinsulinemic, insulin-resistant (Zucker fatty) rats (ZFR) and a related control (Zucker lean) strain (ZLR). Glucose metabolism was characterized by minimal model analysis of intravenous glucose tolerance test data. Seven-week-old ZFR (n=18) and ZLR (n=17) were studied under pentobarbital anesthesia. Mean body weight and plasma glucose and insulin concentration were significantly greater (P<0.05) in ZFR than in ZLR, whereas basal values of mean arterial pressure (MAP) and heart rate (HR) were not significantly different. Increments of MAP (DeltaMAP) and HR (DeltaHR) elicited by electrical stimulation of the sciatic nerve (5-s trains of 100 pulses, 0.5-ms pulse duration, 100- to 400-microA pulse intensity) were significantly higher (ANOVA, P<0.05) in ZFR at each level of stimulus intensity. Regression analysis showed a linear increase in DeltaMAP and DeltaHR with increasing sciatic nerve stimulus intensity. Pressor responses to phenylephrine after ganglionic blockade demonstrated that vascular reactivity to adrenergic stimulation is not increased in ZFR compared with ZLR. Thus this factor does not contribute to enhancement of somatosympathetic reflexes observed in this strain. Insulin sensitivity in ZFR was one-fourth (P<0.05) that in ZLR. These results suggest that stronger sympathetic nervous reactivity in ZFR is associated with a severe insulin-resistant state before the onset of hypertension and support the hypothesis that insulin-mediated stimulation of the sympathetic nervous system is involved in the development of cardiovascular diseases related to alterations of glucose metabolism.

Measuring transient systemic conductance and capacitance responses using a modified Brooksby-Donald technique in anesthetized, autonomically intact rabbits

BACKGROUND

The Brooksby-Donald approach uses two flow probes to measure the inflow and outflow from an organ or vascular bed; the difference in flow can be time-integrated to assess changes in venous capacitance.

OBJECTIVES

To measure changes in subdiaphragmatic venous capacitance and arterial conductance in acutely instrumented rabbits, and to document the acute vascular responses to intravenous injections of pharmacological agents.

METHODS

In artificially ventilated, fentanyl-anesthetized New Zealand female rabbits, ultrasonic flow probes were attached to the descending thoracic aorta and inferior vena cava to measure subdiaphragmatic inflow and outflow. Systemic arterial and venous pressures were measured. Conductance was calculated as aortic flow divided by the difference between systemic arterial and venous pressures. Changes in capacitance were assessed by integrating flow differences. Nitroglycerin (NG), isoproterenol hydrochloride, phenylephrine hydrochloride (PE) and vasopressin (VP) were administered intravenously in stepwise injections, and transient conductance and capacitance responses were determined.

RESULTS

NG significantly increased conductance and capacitance, while isoproterenol hydrochloride had significant effects only on conductance. Both VP and PE significantly decreased conductance and capacitance.

CONCLUSIONS

The modified Brooksby-Donald approach used in the present study was validated by the observed concordant increases in conductance and capacitance caused by NG, and decreases caused by VP and PE. This approach may be useful to characterize specific comparative conductance-capacitance properties of various vasoactive agents.

Effects of intravenous prostaglandin E1 on arterial compliance: a randomized controlled trial

Background: Prostanoids are in widespread use for the treatment of critical limb ischemia and are suggested to improve arterial compliance. However, dose- and time-dependency of these drug effects are indeterminate. We investigated the influence of intravenous application of prostanoids on arterial compliance parameters in patients with critical limb ischemia due to peripheral artery disease (PAD). Patients and methods: We included 82 consecutive patients with PAD Fontaine stage III and IV in a patient-blinded, randomized controlled trial. Patients were randomly assigned to either single dose intravenous treatment with 40 mug (n = 29) or 60 mug (n = 27) of Alprostadil (PGE1) in 250 ml 0.9% saline over 2 hours, or 250 ml 0.9% saline solution as a placebo group (n = 26). Large and small artery compliance was measured by peripheral pulse contour analysis at baseline, at one hour during intravenous infusion of Alprostadil, immediately after and 24 hours after the end of the infusion. For study purpose the patients received Alprostadil only once during the observation period of 2 days. Results: Large artery compliance, blood pressure, heart rate and cardiac output were unaffected by PGE1 administration irrespectively of drug-dosage or time interval. Small artery compliance increased at 1 hour during intravenous application of Alprostadil (40 mug Alprostadil p = 0.001; 60 mug Alprostadil p < 0.0001) compared to placebo and increased median +47% (IQR +5% to +100%) after administration of 40 mug Alprostadil and median +32% (IQR –11% to +88%) after 60 mug Alprostadil (p = 0.5). Immediately after the end of Alprostadil infusion small artery compliance decreased to baseline levels. Conclusions: Prostaglandin E1 causes a significant improvement of small artery compliance during the time of intravenous application. However, this effect rapidly diminishes after the end of administration and no dose-dependency between 40 mug and 60 mug Alprostadil is observed.

Effect of antihypertensive monotherapy and combination therapy on arterial distensibility and left ventricular mass

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors and calcium channel blockers (CCBs) increase arterial compliance and decrease left ventricular mass in hypertensive patients. This study examined whether combined therapy has greater arterial and cardiac effects than doubled doses of the individual drugs.

METHODS

This prospective, randomized, open-label study enrolled 106 patients aged >/=18 years with mild-to-moderate hypertension. Patients were randomized to 5 mg of amlodipine or 20 mg of benazepril for 2 weeks; then, depending on randomization assignment, they were force-titrated to 10 mg of amlodipine or 40 mg of benazepril monotherapy, or to combination amlodipine (5 mg) and benazepril (20 mg) treatment for 22 weeks. Arterial distensibility was assessed using the DynaPulse ambulatory system, and left ventricular mass was assessed by echocardiography.

RESULTS

Combination therapy (0.71% +/- 0.51% mL/mm Hg) increased arterial distensibility more than amlodipine (0.28% +/- 0.69% mL/mm Hg; P =.008) or benazepril (0.39% +/- 0.62% mL/mm Hg; P =.03) monotherapies. Left ventricular mass decreased more with combination treatment (65 +/- 56 g) than with amlodipine (28 +/- 4 g; P <.02); the difference from benazepril (42 +/- 50 g) was not significant.

CONCLUSIONS

Combined ACE inhibitor and CCB treatment was more efficacious than high doses of the individual agents in increasing arterial compliance and reducing left ventricular mass. These findings indicate that appropriately selected combinations of antihypertensive drugs might have enhanced cardioprotective effects.

Role of endothelin in regulation of resistance, fluid-exchange, and capacitance functions of the systemic circulation

This article reviews data at the in vivo whole animal and human level. The importance of both flow and pressure recordings and of the methods used to record these variables is emphasized. Exogenous administration of endothelin-1 evokes a transient depressor response mediated by endothelial endothelinB receptors, but the predominate effect of endothelin-1 is a sustained increase in blood pressure resulting from increases in total peripheral resistance. Resistance in the superior mesenteric, renal, and hindquarter vascular beds of animals and forearm resistance in humans is increased. Both endothelinA and, to a lesser extent, endothelinB receptors on vascular smooth muscle mediate the increases in resistance. Endothelin-1 evokes decreases in the precapillary/postcapillary resistance ratio, resulting in increased capillary pressure and net transcapillary filtration. Endothelin-1 evokes increases in mean circulatory filling pressure in animals and in constriction of the human dorsal hand vein. This venoconstrictor activity is mediated primarily through endothelinA and to a lesser extent endothelinB receptors. Endogenously generated endothelin contributes to the hemodynamic effects of angiotensin and vasopressin in certain animal models of hypertension. Antagonists of endothelin evoke modest hemodynamic changes in healthy humans and in some healthy animals, and they decrease vascular resistance dramatically in several salt-sensitive rat models of hypertension and also in some hypertensive human subjects. Thus, endogenously generated ET appears to play a modest role in the healthy organism, but it likely plays a major role in many pathophysiological states as described in companion articles in this issue.

Hyperaemic response to cigarette smoking in healthy gingiva

BACKGROUND AND AIM

Cigarette smoking is currently considered as a risk factor for periodontal disease. Controversy exists as to whether the vasoconstrictive property of nicotine is one of the pathogenic mechanisms. To this end we tested the hypothesis that cigarette smoking is causing vasoconstriction in the healthy human gingiva.

MATERIALS AND METHODS

Gingival blood flow was continuously measured with laser Doppler flowmetry in healthy (n=13) casual consumers of tobacco. Simultaneously, recordings were made of skin blood flow in the forehead and the thumb as well as heart rate (HR) and blood pressure (BP). In another session infraorbital nerve block anaesthesia (INB) with 1.0 ml of Carbocain without vasoconstrictive additives was used to identify nervously mediated vascular responses to cigarette smoking (n=8).

RESULTS

Cigarette smoking induced a modest hyperaemic response in the gingiva that was lower than the relative increases in BP and HR, and the calculated gingival vascular conductance decreased. In the forehead, flow responses were similar to those in the gingiva, while in the thumb a powerful vasoconstriction was observed. During the later part of the 10-min recovery period, BP and HR tended to decrease while blood flow in the gingiva and forehead remained high. INB potentiated the hyperaemic response to cigarette smoking in gingiva.

CONCLUSIONS

The present results help to shed some light on the understanding of the vasoactive mechanisms induced by cigarette smoking, and to support the hypothesis that cigarette smoking causes nervously mediated vasoconstriction in the healthy human gingiva. However, the degree of vasoconstriction was far less than in the thumb skin, and in our subjects was overcome by the evoked rise in arterial perfusion pressure. As a consequence, gingival blood flow increased during smoking. It is speculated that small repeated vasoconstrictive attacks due to cigarette smoking may in the long run contribute to gingival vascular dysfunction and periodontal disease.

Relationship between arterial distensibility and low-frequency power spectrum of blood pressure in spontaneously hypertensive rats

The aim of this study was to determine in spontaneously hypertensive rats (SHRs) whether a significant association may be observed between the low-frequency component of blood pressure variability (BPV) and arterial distensibility and to evaluate the role of the autonomic nervous system in this relationship. Doxazosin (1 mg/kg/d s.c.), flesinoxan (1 mg/kg/d s.c.), and urapidil (30 mg/kg/d s.c.) were infused over 24 h in SHRs. Blood pressure was recorded in conscious rats and BPV was characterized by spectral analysis. The distensibility-pressure curves for the carotid artery were determined by an ultrasonic echo-tracking device in anesthetized rats. Untreated SHRs had higher mean arterial pressure (MAP) and low-frequency MAP but a lower distensibility than normotensive Wistar-Kyoto rats. In SHRs inhibition of the autonomic nervous system by peripheral blockade of alpha1-adrenoceptors (doxazosin, 1 mg/kg, or urapidil, 30 mg/kg) or centrally mediated reduction of sympathetic tone (flesinoxan, 1 mg/kg) reduced MAP and low-frequency MAP in the conscious state and increased carotid operational distensibility in the anesthetized state. In these SHRs, we observed a negative association between low-frequency MAP and operational distensibility ( r = -0.48, p < 0.01). From multiple regression analysis, MAP and low-frequency MAP, but not drug treatment, influenced arterial distensibility. Our study in SHRs provides evidence for a strong association between increased low-frequency MAP and reduced arterial distensibility, with a common modulation provided by the autonomic nervous system via the alpha 1 -adrenergic receptor component and central nervous system.

Effect of phosphodiesterase III inhibitor on contractility, afterload, and vascular capacitance during right heart bypass preparation

OBJECTIVES

Phosphodiesterase III inhibitors, which have both positive inotropic and vasodilatory effects, occasionally cause hypotension due to afterload reduction and possibly due to preload reduction caused by the increase in vascular capacitance.

METHODS

Six open-chest adult mongrel dogs were used to compare the effects on left ventricular contractility, afterload, and vascular capacitance of the phosphodiesterase III inhibitor, olprinone, with those of dobutamine using a right-heart-bypass model. Contractility and afterload were evaluated by the left ventricular pressure-volume relations with the use of a conductance catheter to derive the end-systolic elastance (Ees) and the effective arterial elastance (Ea). Vascular capacitance change was evaluated by reservoir volume change under a constant bypass flow (80 ml/kg per minute).

RESULTS

Ees increased significantly both with dobutamine (7.6 +/- 2.8 to 14.3 +/- 4.8 mmHg/ml, p < 0.05) and with olprinone (7.6 +/- 2.9 to 11.5 +/- 4.2 mmHg/ml, p < 0.05). Ea did not change with dobutamine (14.4 +/- 3.5 to 14.5 +/- 3.6 mmHg/ml, p = 0.9), whereas it decreased with olprinone (14.0 +/- 4.1 to 11.4 +/- 3.8 mmHg/ml, p = 0.093). Reservoir volume increased after the infusion of dobutamine (-94.0 +/- 39.8 ml), and decreased after the infusion of olprinone (-114.0 +/- 62.3 ml). The difference was statistically significant (p = 0.007). The reservoir volume change indicated that vascular capacitance decreased with dobutamine, and increased with olprinone.

CONCLUSIONS

Pre- and afterload reduction of olprinone combined with the positive inotropic effect are useful in treating congestive heart failure and managing low cardiac output syndrome after cardiac surgery.

Hindlimb unweighting affects rat vascular capacitance function

Microgravity is associated with an impaired stroke volume and, therefore, cardiac output response to orthostatic stress. We hypothesized that a decreased venous filling pressure due to increased venous compliance may be an important contributing factor in this response. We used a constant flow, constant right atrial pressure cardiopulmonary bypass procedure to measure total systemic vascular compliance (C(T)), arterial compliance (C(A)), and venous compliance (C(V)) in seven control and seven 21-day hindlimb unweighted (HLU) rats. These compliance values were calculated under baseline conditions and during an infusion of 0.2 microg*kg(-1)*min(-1) norepinephrine (NE). The change in reservoir volume, which reflects changes in unstressed vascular volume (DeltaV(0)) that occurred upon infusion of NE, was also measured. C(T) and C(V) were larger in HLU rats both at baseline and during the NE infusion (P < 0.05). Infusion of NE decreased C(T) and C(V) by ~20% in both HLU and control rats (P < 0.01). C(A) was also significantly decreased in both groups of rats by NE (P < 0.01), but values of C(A) were similar between HLU and control rats both at baseline and during the NE infusion. Additionally, the NE-induced DeltaV(0) was attenuated by 53% in HLU rats compared with control rats (P < 0.05). The larger C(V) and attenuated DeltaV(0) in HLU rats could contribute to a decreased filling pressure during orthostasis and thus may partially underlie the mechanism leading to the exaggerated fall in stroke volume and cardiac output seen in astronauts during an orthostatic stress after exposure to microgravity.

[Effect of taurine on the microvessel exchange function and adrenergic response of veins and arteries in the cat skeletal muscle]

In cats anesthetized with Uretan and perfused with a constant blood volume, Taurine induced responses of neither arterial nor venous vessels of the skeletal muscle but increased the capillary filtration coefficient without any significant change of the capillary pressure in the skeletal muscle's microvessels. Taurine also increased both the constrictor and the dilatory responses of the arterial and venous vessels. The mechanism of the Taurine effects upon the smooth muscle elements of arteries and veins as well as upon proper mechanisms of capillary pressure control and capillary filtration coefficient, seems to be calcium-dependent.

Constriction to ETB receptor agonists, BQ-3020 and sarafotoxin s6c, in human resistance and capacitance vessels in vivo

AIMS

The aim of the study was to examine the effects of the ETB receptor selective agonists sarafotoxin S6c (SFTX6c) and BQ-3020 on the forearm resistance and capacitance vessels in healthy subjects in vivo.

METHODS

The local response to intra-arterial or intravenous infusion of SFTX6c (5 pmol min-1) or BQ-3020 (50 pmol min-1) was assessed, on separate occasions, in eight healthy men (aged 20-28 years). Data (mean +/- s.e.mean) were examined by ANOVA. Results are expressed as percentage change from baseline at 90 min.

RESULTS

SFTX6c and BQ-3020 reduced forearm blood flow, following local intra-arterial infusion (-25 +/- 7% and -27 +/- 7%, respectively; P < 0.001) and reduced hand vein diameter, following local intravenous infusion (-30 +/- 8% and -16 +/- 7%, respectively; P < 0.001).

CONCLUSIONS

We have shown that locally active infusions of the selective ETB receptor agonists SFTX6c and BQ-3020 cause arterial constriction and venoconstriction in healthy human blood vessels in vivo. These results indicate that ETB receptor stimulation may mediate vasoconstriction in humans.

Intradialytic and interdialytic effects of treatment with 1.25 and 1. 75 Mmol/L of calcium dialysate on arterial compliance in patients on hemodialysis

Arterial compliance (AC) is an important determinant of vascular structure, and abnormalities of AC can greatly affect the cardiovascular system. Given the vasoconstrictive properties of increased levels of serum ionized calcium (iCa), we investigated the way that dialysate calcium level can influence AC in the hemodialysis (HD) population. In a crossover randomized design, 19 dialysis patients undergoing regular bicarbonate HD (three times weekly) underwent two cycles of four successive HD sessions each with a low (LdCa; 1.25 mmol/L) and high dialysate calcium concentration (HdCa; 1.75 mmol/L). At the fourth session of each cycle, iCa level and hemodynamic parameters (systolic blood pressure [SBP], diastolic blood pressure, mean arterial pressure [MAP], pulse pressure [PP], heart rate, and AC) were measured pre-HD and post-HD. AC was measured noninvasively at the brachial artery by arterial pulse waveform analysis. The dialysate calcium level was a significant determinant of both pre-HD (r = 0.335; P < 0.05) and post-HD iCa level (r = 0.767; P < 0.001). Pre-HD AC increased significantly (P < 0.05) by 0.01+/- 0.02 mL/mm Hg (7% +/- 19%) on switching from HdCa to LdCa treatment. Multiple regression analysis showed that both pre-HD PP and iCa level were major inverse determinants of pre-HD AC in both the LdCa (R(2) = 0.65; P < 0.001) and HdCa (R(2) = 0.51; P < 0.01) treatment groups. AC increased by 32% (P < 0.01) and 37% (P < 0.05) during LdCa and HdCa dialysis, respectively. Intradialytic changes in AC were inversely correlated with changes in SBP and PP. In the HdCa group, changes in iCa level related significantly to MAP (r = 0.464; P < 0.05). The results show that changes in AC during HD are mainly mediated through concurrent changes of systemic hemodynamics, which are largely affected by dialysate calcium level through parallel changes in iCa level. Interdialytically, a significant, blood pressure-independent, inverse relationship between AC and iCa level exists. Therefore, HD with LdCa, by reducing the incidence of HD-induced hypercalcemia, may have a beneficial role in preventing the ongoing reduction of AC in HD patients and thus improving cardiovascular prognosis.

Effect of somatostatin on resistance and on capacitance rabbit isolated arteries

The effects of somatostatin, a tetradecapeptide isolated from hypothalamus extracts, were studied on the vascular reactivity of aorta and mesenteric arteries isolated from rabbits. We also investigated whether or not Ca(2+) movements were implicated in these effects. Rabbit aorta and mesenteric (fifth branch) arteries were isolated, cleaned off, and mounted in an organ bath containing Godfraind solution or physiological saline solution (PSS), respectively. Somatostatin (10(-8)-10(-4) M) produced a concentration-dependent inhibition of the contractile responses induced by high K(+) (80 mM) or noradrenaline (10(-6) M in aorta or 10(-4) M in mesenteric arteries) in both arteries studied. The inhibitory effect of somatostatin was greater in mesenteric resistance vessels (IC(50) 3.1+/-2.3x10(-5) M, and 5.2+/-4.8x10(-8) M with KCl and noradrenaline, respectively). Contractile responses produced by the addition of Ca(2+) (1-5 mM) to Ca(2+)-free high K(+) solution were also concentration dependently inhibited by somatostatin in aorta. Furthermore, somatostatin decreased noradrenaline-induced contraction attributed to intracellular Ca(2+) release in aorta, and inhibited 45Ca(2+) uptake stimulated by high K(+) or by noradrenaline. However, it did not modify 45Ca(2+) uptake in resting mesenteric resistance arteries. Taken together, these results suggest that somatostatin exerts an inhibitory effect on vascular contractions induced by some stimulating agents in different arteries isolated from rabbits, being more potent in mesenteric arteries.

Cardiovascular responses of perimenopausal women to hormonal replacement therapy

OBJECTIVE

This study was undertake to test the hypothesis that hormone replacement therapy alters cardiovascular function during the first several months of therapy.

STUDY DESIGN

Serial estimates of blood pressure, heart rate, stroke volume, and venous capacitance were obtained before and at 1, 5, 9, and 21 weeks after the beginning of hormone replacement therapy with daily estradiol and intermittent norethindrone. Measurements were performed by means of electrocardiography, automated blood pressure measurement (Dynamap; Critikon Company LLC, Tampa, Fla), echocardiography, and plethysmography.

RESULTS

Hormone replacement therapy did not alter heart rate, blood pressure, or venous capacitance. End-diastolic volume and stroke volume were unchanged after 1 week of hormone replacement therapy but rose thereafter. After 5 weeks of hormone replacement end-diastolic volume and stroke volume were increased by 13 +/- 5 mL and 9 +/- 2 mL, respectively, and after 9 weeks the increases totaled 23 +/- 5 mL and 17 +/- 3 mL, respectively. As a result cardiac output rose progressively to a level 1.1 +/- 0.3 L/min (18%) greater than pretreatment values and systemic vascular resistance fell 15%. These changes were associated with a 3-fold increase in serum estradiol levels.

CONCLUSION

The studied regimen of hormone replacement therapy produces progressive cardiac remodeling and peripheral vasodilatation during the first 2 months of therapy.

Effect of long-term beta-blockade on aortic root compliance in patients with Marfan syndrome

BACKGROUND

This study was undertaken to assess the effect of long-term beta-blockade on the aortic root stiffness index and distensibility in patients with Marfan syndrome.

METHODS

Aortic root stiffness index and distensibility were calculated according to the formulas of Stefanadis and Hirai, respectively, with 2-dimensional guided M-mode echocardiogram before and after an average of 26 months of atenolol administration.

RESULTS

Twenty-three asymptomatic patients were studied (11 men and 12 women, aged 31 +/- 14.2 years). The follow-up was 4 +/- 2.2 years. The dose of atenolol was individualized (mean 43.5 +/- 21.6 mg/d). Heart rate decreased from 79 +/- 9 beats/min to 64 +/- 9 beats/min (P =. 01), and systolic blood pressure decreased from 124 +/- 13 mm Hg to 114 +/- 2 mm Hg (P =.01). Distensibility increased from 1.85 +/- 0. 70 x 10(-6) cm2/dynes-1 to 2.21 +/- 0.76 x 10-6 cm2/dynes-1 (P =.02), and the stiffness index decreased from 9.68 +/- 3.78 to 8.85 +/- 3. 15 ( P =.2). Two groups of responses to treatment were identified. Compared with baseline values 15 (65%) patients who responded to treatment had increased distensibility and decreased stiffness index of the aortic root (P =.05). Eight patients (35%) who did not respond to treatment had no significant change. Body weight >91 kg and baseline end-diastolic aortic root diameter >40 mm were significantly associated with no response (P =.05). Two patients in the nonresponding group had echocardiographic progression of aortic insufficiency.

CONCLUSIONS

There was a heterogeneous response in the aortic root elastic properties after long-term treatment with atenolol in asymptomatic patients with Marfan syndrome. Stiffness index and distensibility are more likely to respond when the baseline end-diastolic aortic root diameter is <40 mm.

Changes in systemic and regional haemodynamics during 5-HT7 receptor-mediated depressor responses in rats

The 5-hydroxytryptamine (5-HT)-induced late depressor response in rats is mainly mediated by vascular 5-HT7 receptors. The present study was devoted to determining the systemic and regional haemodynamic changes during this response, with particular emphasis on localising vascular beds that may contribute to the increase in total systemic vascular conductance. In vagosympathectomised, pentobarbital-anaesthetised rats pretreated with the 5-HT2 receptor antagonist ritanserin (50 microg kg(-1), i.v.), 5-HT (1, 3 and 10 ug kg(-1) min(-1) during 10 min; i.v.) produced a dose-dependent decrease in mean arterial blood pressure by up to 46+/-3%. This decrease was accompanied by increases in systemic vascular conductance by up to 83+/-15%; cardiac output was unaffected. 5-HT increased regional vascular conductance in skeletal muscle, carcass, mesentery/pancreas and adrenals by up to 740+/-14%, 117+/-18%, 135+/-26% and 88+/-22%, respectively, but decreased 'lung' (mainly arteriovenous anastomotic) conductance by up to 81+/-2%. Pretreatment with R(+)lisuride (100 microg kg(-1), i.v.) abolished all 5-HT-induced systemic and regional haemodynamic effects. In contrast, i.v. pretreatment with S(-)lisuride (100 microg kg(-1)) or GR127935 (300 microg kg(-1)) did not affect the 5-HT-induced systemic haemodynamic changes. The above results suggest that hypotension induced via 5-HT7 receptor activation was exclusively caused by vasodilatation of the systemic vasculature, confined to skeletal muscle, carcass, mesentery/pancreas and adrenal vascular beds. Furthermore, this study shows that blockade of vasorelaxant 5-HT7 receptors by lisuride is stereoselective.

Propofol-induced increase in vascular capacitance is due to inhibition of sympathetic vasoconstrictive activity

BACKGROUND

Venodilation is thought to be one of the mechanisms underlying propofol-induced hypotension. The purpose of this study is to test two hypotheses: (1) propofol increases systemic vascular capacitance, and (2) the capacitance change produced by propofol is a result of an inhibition of sympathetic vasoconstrictor activity.

METHODS

In 33 Wistar rats previously anesthetized with urethane and ketamine, vascular capacitance was examined before and after propofol infusion by measuring mean circulatory filling pressure (Pmcf). The Pmcf was measured during a brief period of circulatory arrest produced by inflating an indwelling balloon in the right atrium. Rats were assigned into four groups: an intact group, a sympathetic nervous system (SNS)-block group produced by hexamethonium infusion, a SNS-block + noradrenaline (NA) group, and a hypovolemic group. The Pmcf was measured at a control state and 2 min after a bolus administration of 2, 10, and 20 mg/kg of propofol.

RESULTS

The mean arterial pressure (MAP) was decreased by propofol dose-dependently in intact, hypovolemic, and SNS-block groups, but the decrease in MAP was less in the SNS-block group (-25%) than in the intact (-50%) and hypovolemic (-61%) groups. In the SNS-block + NA group, MAP decreased only at 20 mg/kg of propofol (-18%). The Pmcf decreased in intact and hypovolemic groups in a dose-dependent fashion but was unchanged in the SNS-block and SNS-block + NA groups.

CONCLUSIONS

The results have provided two principal findings: (1) propofol decreases Pmcf dose-dependently, and (2) the decrease in Pmcf by propofol is elicited only when the sympathetic nervous system is intact, suggesting that propofol increases systemic vascular capacitance as a result of an inhibition of sympathetic nervous system.

Vascular and cardiac effects of amlodipine in acute heart failure in dogs

BACKGROUND

Amlodipine improves exercise capacity in patients with chronic congestive heart failure (HF), but the mechanisms of this effect are unknown.

OBJECTIVE

To test the hypothesis, in a canine model of acute, ischemic HF, that amlodipine increases vascular capacitance and reduces cardiac filling pressures.

METHODS

Amlodipine was given to 13 anesthetized, splenectomized dogs (six controls and seven with HF). Aortic, left ventricular end-diastolic (LVEDP) and portal venous (Pportal) pressures, cardiac output, portal flow (ultrasonic probe) and intestinal blood volume (IBV, 99mTc blood-pool scintigraphy) were measured. Intestinal vascular conductance (= 1/resistance) and vascular capacitance (CAP) were measured before and 15 mins after repetitive 150 micrograms/kg dosages of amlodipine (maximum cumulative dosage, 1000 micrograms/kg). Pportal-IBV curves were obtained by impeding portal flow (pneumatic cuff), and change in CAP was defined by the change in IBV at Pportal = 7.5 mmHg. HF was induced by microsphere embolization of the left coronary artery.

RESULTS

CAP increased in the control group (+ 28%, P < 0.01) but decreased (-9%, P < 0.05) in the HF group. Left ventricular stroke work increased in the control group (P < 0.05), while it decreased (P < 0.05) in the HF group, suggesting a negative inotropic effect. In the control group, LVEDP increased after amlodipine was given (P < 0.05) but did not change significantly in the HF group.

CONCLUSIONS

In the acute experimental HF model, amlodipine failed to increase intestinal vascular CAP or decrease filling pressures, and may have had a negative inotropic effect. The experiment failed to demonstrate a beneficial hemodynamic effect of amlodipine in acute HF, and the mechanism of benefit of this agent in chronic HF remains unclear.

Vascular reactivity is impaired in genetic females taking high-dose androgens

OBJECTIVE

To assess the vascular effects of high-dose androgen treatment in genetic females.

BACKGROUND

Male gender is an independent risk factor for coronary artery disease, suggesting either a protective effect of estrogens and/or a deleterious effect of androgens. We have recently demonstrated that androgen deprivation is associated with enhanced vascular reactivity in adult men, however, the effects of androgen excess on vascular function in humans has not been reported previously.

METHODS

We studied vascular reactivity in two groups of genetic females: 12 female-to-male transsexuals receiving long-term high-dose androgens, and 12 healthy female control subjects, matched for age and smoking history. Using external vascular ultrasound, brachial artery diameter was measured at rest, after flow increase (leading to flow-mediated dilatation [FMD], which depends on normal endothelial function) and after sublingual nitroglycerin (NTG), an endothelium-independent dilator.

RESULTS

Testosterone levels were higher (15.2+/-8.7 vs. 1.9+/-1.3 mmol/L, p < 0.001) and high-density lipoprotein cholesterol levels were lower (1.2+/-0.2 vs. 1.6+/-0.4 mmol/L, p=0.02) in the transsexuals compared with the control subjects. In each group, nine of 12 subjects were current or ex-smokers, leading to impaired FMD in both groups (5.1+/-3.7% in the transsexuals vs. 6.9+/-4.1% in controls, p=0.28). The NTG response was significantly decreased in the transsexuals (15.9+/-4.9% vs. 22+/-5.8% in controls, p=0.01), independent of the effects of age, cholesterol or vessel size.

CONCLUSIONS

Long-term treatment with high-dose androgens is associated with impaired vascular reactivity in genetic females, consistent with a deleterious effect of androgen excess on arterial physiology.

[Contractile adrenergic responses of the arterial and venous vessels and transcapillary fluid exchange in the cat small intestine during taurine administration]

Taurine induced no responses of the intestine arterial and venous vessels in cats. Following the taurine administration, a decrease of the capillary filtration coefficient occurs against the background of the capillary pressure in the intestine microvessels, and adrenergic constrictor responses of the vessels are enhanced. The latter responses reduced with verapamil infusion become again enhanced following taurine administration.

Influence of aging on arterial compliance

With aging, pulse pressure increases. A high pulse pressure has been recognised as an important cardiovascular risk factor. The increase in pulse pressure with aging is mainly due to a decrease in large artery compliance. Compliance and distensibility are large artery wall properties. Compliance is the buffering capacity of the vessel. Distensibility reflects much more the elasticity of the artery. Compliance is related to distensibility and arterial diameter. These large artery wall properties can be measured non-invasively using new echo-tracking techniques. With these techniques it has been shown that the elasticity (distensibility) and the buffering capacity (compliance) of the common carotid artery is decreasing with aging, while diameter of the artery increases. This increase in diameter might be a compensating mechanism to limit the decrease in compliance. There are indications that the effect of aging on large artery wall properties may not be similar at all vascular territories. A decrease in compliance leads to a high pulse pressure and isolated systolic hypertension. The drug of choice for the treatment of isolated systolic hypertension should increase large artery compliance with no, or only minor effect on resistance vessels. This would lead to a decrease in pulse pressure without decreasing mean blood pressure. As a result, systolic but not diastolic blood pressure decreases. It appears that nitrates better than other anti-hypertensive drugs can decrease pulse pressure. They therefore have been advocated for the treatment of isolated systolic hypertension.

[The capacitance function of vessels of the anterior vena cava region during depressor stimulus effects on the blood circulation system]

Depressing neurogenic and humoral (acetylcholine, papaverine and histamine) effects against the background of dilatation of arterial vessels were shown to exert different results: the former stimuli led to blood output from the veins, whereas humoral stimuli enhanced the depot role of the veins in animals. The smallest possible doses of acetylcholine did sometimes reduce the vessels' capacity.

Effect of aerosolized acetylcholine on bronchial blood flow

We studied the effects of aerosolized as well as intravenous infusion of acetylcholine on bronchial blood flow in six anesthetized sheep. Intravenous infusion of acetylcholine, at a dose of 2 microg/kg, increased bronchial blood flow from 45 +/- 15 (SE) to 74 +/- 30 ml/min, and vascular conductance increased by 76 +/- 22%. In contrast, aerosolized acetylcholine at doses of 2 and 20 microg/kg decreased bronchial vascular conductance by approximately 10%. At an aerosolized dose of 200 microg/kg, the bronchial vascular conductance increased by approximately 15%, and there was no further increase in conductance when the aerosolized dose was increased to 2,000 microg/kg. Pretreatment of animals with a nitric oxide synthase inhibitor, Nomega-nitro-L-arginine methyl ester hydrochloride, partially blocked the vasodilatory effects of intravenous acetylcholine and completely blocked the vasodilatory effects of high-dose aerosolized acetylcholine. These data suggest that aerosolized acetylcholine does not readily penetrate the vascular wall of bronchial circulatory system and, therefore, has minimal vasodilatory effects on the bronchial vasculature.

Acute effects of toborinone on vascular capacitance and conductance in experimental heart failure

BACKGROUND

Toborinone (OPC-18790), a phosphodiesterase III inhibitor, enhances cardiac contractility and is an arterial dilator. However, its effects on the venous system have not yet been clearly defined. Because toborinone administration reduces left ventricular (LV) end-diastolic pressure, it is probably also a venodilator. Because of the known arterial effects and the hypothesized venous effects, we compared changes in systemic vascular conductance (the inverse of resistance) with changes in venous capacitance.

METHODS AND RESULTS

In 15 anesthetized, splenectomized dogs (10 treatment, 5 control), pressures were measured in the right atrium, aorta, portal vein, and LV. A cuff constrictor was placed around the portal vein. Cardiac output was measured by thermodilution, and splanchnic vascular capacitance was measured by blood-pool scintigraphic methods. Data were collected at baseline, after induction of heart failure (microsphere embolization into the left coronary artery), and then after toborinone boluses of 0.1, 0.2, 0.4, and 0.8 mg/kg. Heart failure was associated with decreased capacitance and conductance (to 87+/-3% and 64+/-4% of baseline values, respectively, P<0.05). After administration of the lower doses of toborinone, capacitance increased more than conductance; however, the effects were more balanced at the higher doses. Compared with nitroglycerin, hydralazine, and enalaprilat (results of an earlier study) in the same model, toborinone increased capacitance to a degree similar to that with nitroglycerin, at higher doses increased conductance similarly to hydralazine, and increased both capacitance and conductance considerably more than did enalaprilat.

CONCLUSIONS

Toborinone is a potent balanced venous and arterial dilator in experimental acute heart failure. These marked effects suggest that it may prove to be a clinically important alternative to other vasodilators.

Zaprinast, a type V phosphodiesterase inhibitor, dilates capacitance vessels in anaesthetised rats

The effects of zaprinast (a type V phosphodiesterase inhibitor) on mean arterial pressure, heart rate, cardiac output, mean circulatory filling pressure, arterial and venous resistances were compared to those of sodium nitroprusside in three groups, each of intact or ganglion-blocked, Inactin-anaesthetised rats. In intact rats, zaprinast (1.5, 3.0 mg kg(-1) min(-1)) and sodium nitroprusside (8.0, 64.0,microg kg(-1) min(-1)) dose-dependently reduced mean arterial pressure and arterial resistance, but did not alter cardiac output and venous resistance. Both increased heart rate, with the effect of zaprinast less than that of sodium nitroprusside. Mean circulatory filling pressure was elevated by both doses of zaprinast but only the high dose of sodium nitroprusside. In rats given mecamylamine (3.7 micromol kg(-1), i.v. bolus) and noradrenaline (7.3 nmol kg(-l) min(-1)), zaprinast and sodium nitroprusside elicited dose-dependent reductions in mean arterial pressure, arterial and venous resistances, and mean circulatory filling pressure. Both increased cardiac output, with the effect of zaprinast greater than that of sodium nitroprusside at the low dose. Zaprinast but not sodium nitroprusside reduced heart rate. Our results indicate that zaprinast, similar to sodium nitroprusside, dilates both resistance and capacitance vessels in ganglion-blocked rats infused with noradrenaline to restore vasomotor tone. Zaprinast but not sodium nitroprusside has a direct, negative chronotropic effect on the heart.

Effect of felodipine on arterial blood flow and venous function at rest in patients with mild essential hypertension

Felodipine is a second-generation dihydropyridine calcium antagonist used to treat mild to moderate arterial hypertension. The authors used venous occlusion plethysmography to study the effect of this drug on lower limb arterial inflow and venous outflow in 10 at rest patients with mild essential hypertension. They also sought correlations between changes in district blood flow and blood pressure. Plethysmography was carried out at 8 AM and 4, 8, and 24 hours later at baseline (after washout), on the first day of treatment with a single daily administration of 10 mg felodipine ER, and after 7 and 30 days of treatment. The drug was given after the 8 AM evaluation. The authors determined rest flow, maximal venous incremental volume (MVIV) at 40 mmHg and 60 mmHg, and gradient of venous volume between 60 and 40 mmHg divided by the pressure difference (DV/DP) as index of venous distensibility. On the days of plethysmographic evaluation, arterial blood pressure and heart rate were measured continuously over 24 hours by the ABPM (Ambulatory Blood Pressure Monitoring). The results were analyzed by ANOVA. Rest flow, MVIV, and DV/DP were stable at the baseline evaluation. On days 1, 7, and 30 of treatment the rest flow after 4 and 8 hours was significantly greater than at 8 AM but had always returned to normal after 24 hours. No other plethysmographic parameters changed significantly; in particular venous outflow remained unchanged. Mean arterial, systolic, and diastolic blood pressure were significantly reduced, compared with baseline, following treatment on the first day and after 7 and 30 days' treatment. There was no effect on heart rate. The authors conclude that felodipine is useful for the treatment of mild essential hypertension, since it reduces arterial resistance without altering venous capacitance or distensibility.

Catecholaminergic regulation of venous function in the rainbow trout

The significance of the sympathetic nervous system (SNS) in regulating peripheral vascular resistance and cardiac function in fish has been well established, whereas its effect on venous function in vivo is unknown. Two protocols were employed in the present study to evaluate SNS effects on the venous system in intact, unanesthetized trout. In the first, trout were instrumented with pressure cannulas in the ventral (PVA) and dorsal (PDA) aortas and ductus Cuvier (PVEN), and cardiac output (CO) was measured with a flow probe around the ventral aorta. Heart rate, stroke volume, and gill and systemic resistances were calculated from the measured parameters. In the second group, vascular capacitance curves were obtained by monitoring mean circulatory filling pressure (PVEN) during transient interruption of CO and while blood volume was adjusted between 80 and 120% of normal. Unstressed blood volume (USBV) and vascular compliance (C) were derived from the capacitance curves. Infusion of epinephrine (Epi; 3.3 nmol.min-1.kg body wt-1) increased PVA, PDA, and PVEN, whereas norepinephrine (NE) infusion (3.3 nmol.min-1.kg body wt-1) increased PVA and PDA but did not affect PVEN. Epi (1.0 nmol.min-1.kg body wt-1), but not NE (2.6 or 10.4 nmol.min-1.kg body wt-1), displaced the capacitance curve to the right and significantly decreased USBV. Inhibition of alpha 1-adrenoceptors with prazosin, or ganglionic nicotinic receptor blockade with hexamethonium, produced a left shift in the capacitance curve, and both treatments increased USBV and C. Conversely, the alpha-adrenoceptor antagonist phentolamine did not effect vascular capacitance. These results show that Epi has potent effects on trout veins in vivo and that it mobilizes blood from the unstressed into the stressed vascular compartment and augments central venous pressure by decreasing venous compliance. These results also show that the SNS is an active effector of venous tone and compliance in trout; this is the first demonstration of tonic regulation of vascular capacitance in any fish.

Effects of volatile anesthetic agents on in situ vascular smooth muscle transmembrane potential in resistance- and capacitance-regulating blood vessels

INTRODUCTION

This study was designed to compare the inhibitory effect of inhaled volatile anesthetic agents on in situ sympathetic neural versus nonneural regulation of vascular smooth muscle transmembrane potentials as correlates of vascular smooth muscle tone in resistance- and capacitance-regulating blood vessels.

METHODS

Vascular smooth muscle transmembrane potentials were measured in situ with glass microelectrodes in neurally intact, small (200-300 m OD) mesenteric arteries and veins of rats before, during, and after inhaled halothane, isoflurane, or sevoflurane (0.5 or 1.0 minimum alveolar concentration [MAC]). Such transmembrane potentials and their anesthetically induced changes were compared, respectively, with those measured in similar vessel preparations after local sympathetic neural denervation with 6-hydroxydopamine.

RESULTS

In neurally intact vessels, transmembrane potentials (in millivolts, mean +/- SD) before inhalation of the anesthetic agent were -39 +/- 2.8 (artery) and -43 +/- 4.6 (vein). At 1.0 MAC, halothane, isoflurane, and sevoflurane induced respective hyperpolarizations (in millivolts, mean +/- SD) of 9 +/- 3.1, 6 +/- 2.7, and 9 +/- 4.0 in arteries and 6 +/- 4.4, 2.8 +/- 3.0, and 8.7 +/- 5.6 in veins. Sympathetic denervation significantly attenuated these hyperpolarizations (except for venous response to isoflurane). At 0.5 MAC, transmembrane potential responses to all three volatile anesthetic agents were small and not consistently significant in either the intact or denervated vessels.

CONCLUSIONS

In resistance-regulating arteries in situ, inhaled halothane, isoflurane, and sevoflurane (1.0 MAC) attenuate both sympathetic neural and nonneural regulation of vascular smooth muscle transmembrane potentials (and tone). In capacitance-regulating veins in situ, sevoflurane (1.0 MAC) also attenuates both regulatory mechanisms, whereas halothane and isoflurane primarily attenuate nonneural mechanisms. At 0.5 MAC, none of these agents significantly affected either mode of regulation of vascular smooth muscle transmembrane potentials in arteries or veins.

Beta-adrenoceptors in vascular capacitance responses to unloading of carotid baroreceptors in anesthetized dogs

The role of beta- and alpha-adrenoceptors in the total vascular capacitance responses to changing pressure in vascularly isolated carotid sinuses of anesthetized and atropinized dogs was investigated. A change in vascular capacitance was determined by measuring the shift of blood in and out of a reservoir that was connected to the aorta and maintained at a constant pressure. Changes in carotid sinus pressure from 135 to 57 mmHg and back to 137 mmHg resulted in a rapid vascular capacitance response of approximately 30 ml in the absence of adrenoceptor antagonists. Administration of a beta2-adrenoceptor antagonist (ICI-118551) caused a significant enhancement of the capacitance responses to similar decreases and increases in carotid sinus pressure (approximately 130%). Administration of a beta1-adrenoceptor antagonist (CGP-20712A) did not cause any further enhancement of the responses. However, an alpha-blocker (phentolamine) reduced the responses by 75%. The results suggest that in the presence of a beta2-adrenoceptor antagonist vascular capacitance responses to loading and unloading of baroreceptors are greatly enhanced and that patients suffering from orthostatic syncope may benefit from this kind of drug.

Effects of natriuretic peptides and nitroprusside on venous function in trout

Active venous regulation of cardiovascular function is well known in mammals but has not been demonstrated in fish. In the present studies, the natriuretic peptides (NP) rat atrial natriuretic peptide (ANP) and trout ventricular natriuretic peptide (VNP), clearance receptor inhibitor SC-46542, and sodium nitroprusside (SNP) were infused into unanesthetized trout fitted with pressure cannulas in the ventral aorta, dorsal aorta, and ductus Cuvier, and a ventral aorta (VA) flow probe was used to measure cardiac output (CO). In another group, in vivo vascular (venous) capacitance curves were obtained during ANP or SNP infusion. The in vitro effects of NP on vessels and the heart were also examined. ANP, VNP, and SC-46542 decreased central venous pressure (PVen), CO, stroke volume (SV), and gill resistance (RG), whereas systemic resistance (RS) and heart rate (HR) increased. Dorsal aortic pressure (PDA) transiently increased and then fell even though RS remained elevated. ANP decreased mean circulatory filling pressure (MCFP), increased vascular compliance at all blood volumes, and increased unstressed volume in hypovolemic fish. ANP had no direct effect on the heart. ANP responses in vivo were not altered in trout made hypotensive by prior treatment with the angiotensin-converting enzyme inhibitor lisinopril. SNP reduced ventral aortic pressure (PVA), PDA, and RS, increased CO and HR, but did not affect PVen, SV, or RG. SNP slightly decreased MCFP but did not affect compliance or unstressed volume. In vitro, large systemic arteries were more responsive than veins to NP, whereas SNP relaxed both. These results show that, in vivo, NP decrease venous compliance, thereby decreasing venous return, CO, and arterial pressure. Conversely, SNP hypotension is due to decreased RS. This is the first evidence for active regulation of venous capacitance in fish, which probably occurs in small veins or venules. The presence of venous baroreceptors is also suggested.

The effects of cross-linked hemoglobin on regional vascular conductance in dogs

Hemoglobin (Hgb) solutions cause systemic vasoconstriction, which might limit their use as intraoperative blood substitutes. This constriction is thought to be caused by interaction between Hgb and nitric oxide (NO). To determine whether alpha-alpha cross-linked hemoglobin (XL-Hgb) interferes with NO-mediated vasodilation caused by acetylcholine (ACh) and sodium nitroprusside (NTP), we infused these compounds into the femoral, superior mesenteric, and circumflex coronary arteries of anesthetized dogs (n = 6) before and after partial exchange transfusion with XL-Hgb. Additional animals (n = 6) were studied after treatment with 5% albumin. XL-Hgb administration increased mean arterial pressure (MAP) from 81 +/- 5 to 112 +/- 8 (P < 0.05). Albumin reduced MAP from 84 +/- 4 mm Hg to 76 +/- 4 mm Hg (P < 0.05). Vascular conductance after XL-Hgb decreased in the femoral artery, was not changed in the mesenteric bed, and increased modestly in the coronary artery (from 0.19 +/- 0.03 to 0.26 +/- 0.02 mL x mm Hg(-1) x min(-1), P < 0.05). After albumin, conductance was unchanged in the femoral artery and increased in the mesenteric artery. Conductance also increased in the coronary bed (from 0.25 +/- 0.02 to 0.49 +/- 0.03 mL x mm Hg(-1) x min(-1), P < 0.05). The vasodilator response to ACh in the femoral or mesenteric beds was either unaffected or augmented by either XL-Hgb or albumin. In the coronary bed, XL-Hgb blunted the dilator responses to ACh and NTP, while albumin augmented the coronary dilator responses to ACh. In five additional dogs, the NO synthase inhibitor N(G)-monomethyl L-arginine caused MAP to increase from 85 +/- 4 to 90 +/- 8 mm Hg and blunted the coronary dilator responses to ACh by approximately 25%. Subsequent XL-Hgb administration caused a further increase in MAP to 112 +/- 19 mm Hg (P < 0.05) and also further blunted ACh-mediated vasodilator responses in the coronary circulation. XL-Hgb has complex effects on the circulatory system, including a reduction in the vasodilator responses to ACh and NTP in canine coronary arteries in vivo. The potential impact of these events on patients with significant coexisting disease is unclear.

Haemodynamic effects of adrenomedullin in human resistance and capacitance vessels

AIMS

The haemodynamic effects of adrenomedullin and calcitonin gene-related peptide (CGRP) were studied in resistance and capacitance vessels of healthy volunteers.

METHODS

Adrenomedullin and CGRP were infused into the brachial artery of eight healthy subjects on two separate occasions at doses between 0.3-30 pmol min(-1). Forearm blood flow was measured using venous occlusion plethysmography. Venodilatation to adrenomedullin and CGRP was assessed in a further eight subjects by infusing the peptides at doses between 0.3-10 pmol min(-1) into a dorsal hand vein preconstricted with noradrenaline. Venodilator responses were measured as percentage reduction in noradrenaline preconstriction.

RESULTS

Adrenomedullin and CGRP at a dose of 30 pmol min(-1), produced an increase in forearm blood flow of 288 +/- 42% and 252 +/- 30% respectively (mean +/- s.e. mean, P<0.001). At doses between 3 and 10 pmol min(-1) adrenomedullin was significantly more potent than CGRP. The vasodilatation to both peptides was of similar duration with a biological half-life of approximately 18 min. Adrenomedullin reversed constriction in dorsal hand veins by 84 +/- 2% (P<0.001) at a dose of 10 pmol min(-1). CGRP produced a similar effect reversing constriction by 72 +/- 12% at the same dose (P<0.01). In veins, adrenomedullin was also more potent than CGRP at doses between 0.3 and 3 pmol min(-1).

CONCLUSIONS

The lowest dose of adrenomedullin producing significant arteriolar dilatation was calculated to produce plasma levels similar to those found in heart failure. These findings suggest that in pathophysiological conditions such as heart failure circulating levels of adrenomedullin may be within a range capable of influencing vascular resistance directly.

Regional gradation of L-type calcium currents in the feline heart with a healed myocardial infarct

INTRODUCTION

Abnormal action potentials in myocytes adjacent to > 2-month-old feline LV myocardial infarcts (MI) may reflect alterations in Ca2+ currents (Ica).

METHODS AND RESULTS

We compared ICa, at 36 degrees C, in subendocardial myocytes isolated from areas adjacent to MI and to ICa in cells from remote areas (> 4 mm away; REM) and control cells from similar regions in normal hearts. Control (CON) myocytes had membrane capacitance of 234 +/- 10 pF (n = 81 cells) compared to 305 +/- 14 pF in REM (71 cells; P < 0.05 from CON) and 237 +/- 11 pF (n = 55 cells) in MI (not different from CON). From Vh = -40 mV; peak ICa elicited by test potentials (-35 to +70 mV) were significantly larger in CON (-1746 +/- 123 pA) and REM (-1795 +/- 142 pA) compared to MI (-1352 +/- 129 pA) (P < 0.05). Peak ICa density was significantly reduced in REM (-6.0 +/- 0.4 pA/pF) or MI (-5.7 +/- 0.4 pA/pF, P < 0.05) compared to CON (-7.5 +/- 0.4 pA/pF). Double exponential ICa decay was similar among groups. Half-inactivation potential (V0.5) was significantly shifted (hyperpolarizing direction) for MI (-29.1 +/- 2.6 mV) and REM (-24.6 +/- 1.2 mV) myocytes compared to -20.3 +/- 1.0 mV in CON. MI slope factor (k; 9.0 +/- 0.5) was significantly different from CON (6.8 +/- 0.3) and REM (7.3 +/- 0.4). No differences in time course of recovery from inactivation were noted. Five millimolar Ba2+o produced significant increases in ICa in CON and REM but an attenuated response in MI. Bay K8644 (1 microM) produced similar ICa increase in all groups. ICa increase due to isoproterenol (1 microM) in MI and REM was half that in CON, but there were no differences in increased ICa responses among groups following phenylephrine (10 microM).

CONCLUSION

Reduced ICa density in REM reflects cell hypertrophy, whereas altered ICa of MI may reflect altered channel structure and/or function.

[Changes in venous tonus in rats with heart failure during acute and chronic perindopril administration]

The effect of chronic administration of perindopril (given per os daily for 21 days) and a single i.v. injection of perindoprilate (0.5 mg/kg) on the mean circulatory filling pressure (MCFP), mean arterial pressure (MAP), and heart rate (HR) was evaluated in conscious rats with heart failure caused by embolization of the coronary vessels with microspheres 21 days prior to the experiment. In the group of rats with cardiac failure perindoprilate reduced MAP by 10% and MCFP by 15%, but did not change AP and MCFP in animals which had been subjected to a sham-operation. Perindopryl reduced AP by 41% and MCFP by 20% in rats with heart failure, and by 37% and 13%, respectively, in rats which had undergone a sham-operation. It is concluded that the venous vessels in rats with heart failure possess increased sensitivity to perindopril.

Effects of calcium entry blockers on distribution of blood volume

To evaluate the effects on hemodynamics and the distribution of blood volume of various calcium entry blocker (CEB) agents, we invasively studied 24 hypertensive patients before and after treatment with isradipine, diltiazem, and verapamil. All three agents reduced arterial pressure through a significant fall in total peripheral resistance without causing reflex tachycardia, while preserving stroke volume and cardiac output. Verapamil reduced the central blood volume (CBV) and the ratio of CBV to total blood volume (TBV) in the supine position (P < .05), suggesting peripheral venodilatation. Isradipine and verapamil modified the responses to head-up tilt. The orthostatic decrease in stroke volume was accentuated following treatment, and it was associated with a greater fall in the ratio of CBV to TBV, suggesting that these two agents attenuate the reflex venoconstriction induced by postural change. In contrast to verapamil and isradipine, diltiazem did not affect volume distribution in the supine or head-up positions. These results suggest that the effect of CEBs varies in order of venodilatory effect from verapamil to isradipine to diltiazem, with verapamil having the greatest effect.

Effects of progestogens on haemostasis

Epidemiological data suggested an involvement of the progestogen component in the pathomechanism of venous and arterial diseases during intake of oral contraceptives. The influence of progestogens on haemostasis parameters depend on type and dose of the progestogen, the presence of an estrogen, the route of application, and the duration of use. Treatment of women with progestogen-only preparations caused only minor effects on coagulation and fibrinolysis. Similarly, during hormone replacement therapy with natural estrogens, the additional application of progestogens induced no unfavourable changes on haemostasis. In contrast, the use of ovulation inhibitors resulted in an acceleration of coagulation and fibrinolysis. This is primarily induced by the marked action of ethinylestradiol on hepatic and vascular function. Progestogens with androgenic properties may counteract the estrogen-induced changes in the hepatic synthesis of platelet aggregation and readiness for coagulation. Estrogen and progesterone receptors are localized in endothelial and smooth muscle cells of the vessel wall, but there are differences in the response of veins and arteries to sex steroids. Estrogens and progestogens may influence collagen and elastin synthesis, and the release of vasoactive compounds and of factors controlling fibrinolysis from endothelium. In veins, progestogens may increase distensibility and capacitance resulting in a decreased blood flow. In predisposed women, this may lead to venous stasis and thrombosis. In arteries, progestogens may act as vasoconstrictors, and may enhance vasospasms at sites of injured endothelium which finally may lead to ischemic diseases.

Cardiovascular effect of oral calcium supplementation: echocardiographic study in patients with essential hypertension

Oral calcium (Ca) supplementation mildly reduces blood pressure. The authors studied the effects of Ca supplementation on the cardiovascular system in patients with mild to moderate essential hypertension. Twelve patients aged forty-nine to seventy years (7 men and 5 women, mean age with 60.3 +/- 7.2 years) participated. The investigators orally administered Ca (1.0 g/day for one week) under hospitalization, adding to a dietary intake of Ca (0.6 g/day). Left ventricular function and systemic arterial compliance were evaluated by M-mode and pulsed Doppler echocardiographies before and after seven days of Ca supplementation. Left ventricular contractility and afterload were not changed. Preload indicated by end-diastolic volume was significantly decreased after Ca supplementation (109.6 +/- 8.5 vs 107.3 +/- 8.2 mL, P < 0.05). Myocardial relaxation evaluated by IIa-mitral valve opening time (87.7 +/- 6.7 vs 82.1 +/- 6.2 ms, P < 0.01) and maximum descending rate of the left ventricular posterior wall (10.6 +/- 1.0 vs 12.4 +/- 1.0 cm/s, P < 0.01), and atrioventricular net compliance assessed by the descending slope of rapid filling flow in the left ventricular inflow tract (2.63 +/- 0.24 vs 2.26 +/- 0.17 m/s2, P <0.05), as well as systemic arterial compliance (2.05 +/- 0.20 vs 2.73 +/- 0.26 mL/mmHg, P < 0.01) were significantly improved by Ca supplementation. Oral Ca supplementation improved the disturbed left ventricular diastolic function and systemic arterial compliance.

Effect of perindopril in pacing-induced canine models of acute and chronic heart failure

OBJECTIVE

To examine the effects of perindopril, a nonsulfhydryl-containing angiotensin-converting enzyme inhibitor, on total vascular capacitance and hemodynamics in acute and chronic dog models of heart failure.

METHODS

Acute heart failure was induced in anesthetized, splenectomized dogs by a volume load (dextran 70, 20 mL/kg) during rapid right ventricular pacing (RRVP) at 250 beats/min. Pretreatment with perindopril (0.3 mg/kg daily for six days, n = 7) was compared with no treatment (n = 7). Total vascular capacitance and compliance were measured from plots of mean circulatory filling pressure during acetylcholine-induced circulatory arrests at different blood volumes. Chronic heart failure was induced by continuous RRVP in splenectomized dogs treated with perindopril (0.3 mg/kg daily, n = 8), which were compared with untreated dogs (n = 8). Hemodynamics and total vascular capacitance and compliance were measured at baseline and after 33 days of RRVP.

RESULTS

Perindopril treatment did not significantly modify the increased pulmonary capillary wedge and mean circulatory filling pressures, reduced total vascular compliance or total vascular capacitance associated with the volume load and acute RRVP. During chronic RRVP, perindopril reduced weight gain and the development of ascites, reduced right atrial pressure (6.3 +/- 1.3 versus 10.3 +/- 1.2 mmHg), mean circulatory filling pressure (9.3 +/- 1.0 versus 14.7 +/- 1.2 mmHg), stressed blood volume (22 +/- 3 versus 33 +/- 4 mL/kg) and central blood volume (10 +/- 1 versus 14 +/- 1 mL/kg) while increasing cardiac output (122 +/- 9 versus 98 +/- 7 mL/kg). However, the reduction in total vascular capacitance was not attenuated and pulmonary capillary wedge pressure was not lowered significantly (18.5 +/- 1.5 versus 21.4 +/- 1.3 mmHg).

CONCLUSION

Perindopril failed to modify hemodynamics in the pacing-induced canine model of acute heart failure but had beneficial effects in the model of chronic heart failure.

Effects of pinacidil on arterial and venous resistances and mean circulatory filling pressure in rats

1. The effects of the potassium channel opener, pinacidil, on mean arterial pressure (MAP), mean circulatory filling pressure (MCFP), total peripheral resistance (TPR), cardiac output (CO) and resistance to venous return (Rv) were studied in rats. 2. In pentobarbitone-anaesthetized rats given mecamylamine (ganglionic blocker, 3.7 micrograms kg-1) and noradrenaline (1.5 micrograms kg-1 min-1) to suppress autonomic reflexes, pinacidil (60 and 180 micrograms kg-1 min-1), relative to the vehicle, reduced MAP and TPR in a dose-dependent manner but did not significantly alter CO, MCFP or RV. 3. Pinacidil (10-300 micrograms kg-1 min-1) caused similar increases in MCFP, an inverse index of venous compliance, and similar dose-dependent reductions in mean arterial pressure (MAP) in conscious, intact rats and rats infused with the ganglionic blocker, hexamethonium (150 micrograms kg-1 min-1). In rats with vasomotor tone elevated by the infusion of noradrenaline (1.5 micrograms kg-1 min-1), pinacidil caused markedly greater depressor responses but did not significantly alter MCFP. 4. Our results show that pinacidil is an efficacious vasodilator of arterial resistance blood vessels but has little venodilator activity.

[The dependence of ortho- and antiorthostatic hemodynamic reactions on the initial (controllable) tonus of the arterial vessels in rats]

Ortho- and antiorthostatic responses of the hemodynamics were compared by numerous parameters in anesthetised rats. In particular, in antiorthostatism the decrease of diastolic pressure as well as systolic one was greater at a lower initial arterial pressure. The data obtained suggest that, in orthostasis, the constrictor vascular compensatory responses are mainly revealed at a high initial arterial pressure. This mechanism of the compensation is less obvious in antiorthostatism.

Acute effect of L-arginine on hemodynamics and vascular capacitance in the canine pacing model of heart failure

The effect of L-arginine, 250 mg/kg over 10 min, on hemodynamics and venous function was studied in nine splenectomized dogs under light pentobarbital anesthesia before and after 17 +/- 1 days of rapid right ventricular pacing (RRVP) at 250 beats/min. Chronic RRVP induced mild congestive heart failure with increased mean circulatory filling (Pmcf), right atrial (Pra) and pulmonary capillary wedge pressures (Ppcw), and reduced cardiac output (CO). During the development of heart failure, total vascular compliance assessed from Pmcf-blood volume relationships during circulatory arrest was unchanged, but total vascular capacitance was markedly reduced, with an increase in stressed and reduction in unstressed blood volumes. At baseline but not after RRVP, L-arginine increased CO and reduced pulmonary vascular resistance. There were no significant changes in Pra, Ppcw, or total peripheral resistance. L-Arginine failed to alter total vascular compliance and capacitance or central blood volume in the baseline or failure state. These results do not support the hypothesis that increased Pmcf and reduced total vascular capacitance in the early stages of pacing-induced heart failure are caused by reduced substrate availability for or an endogenous competitive antagonist of NO synthase in venous endothelial cells.