Vitamin E restores endothelium dependent vasodilatation in cholesterol fed rabbits: in vivo measurements by photoplethysmography

OBJECTIVE

Pulse curve plethysmography was used to examine the effect of vitamin E on endothelium dependent and independent vasodilatation in unanaesthetised cholesterol fed rabbits in vivo. The height of the dicrotic notch was used as an index of general arterial vasodilatation.

METHODS

Twenty eight rabbits were divided into three study groups; a control group (group 1, n = 8), a group fed 1% cholesterol (group 2, n = 10), and a group fed 1% cholesterol with the addition of 0.2% vitamin E after four weeks (group 3, n = 10). After six weeks on diet the vasodilator responses to acetylcholine and glyceryl trinitrate were measured by photoplethysmography of the rabbit ear. Recordings were made during light sedation at baseline and during infusion of acetylcholine (1.5, 3.0, 6.0, and 12 micrograms.min-1) and glyceryl trinitrate (3.75, 7.5, and 15.0 micrograms.min-1). In a second set of experiments with control fed rabbits (n = 5), acetylcholine infusions were given before and after infusion of L-nitro-arginine (15 mg).

RESULTS

The relative height of the dicrotic notch (which predominantly indicates arterial tone in the larger vessels) was reduced by acetylcholine in a dose dependent manner, but in cholesterol fed rabbits (group 2) this response was significantly decreased. Rabbits receiving concomitant dietary vitamin E responded in a similar manner to controls. The difference was most prominent using acetylcholine at a dose of 3.0 micrograms.min-1, where the mean change from baseline was 11(SEM 4)% in group 2, compared to 31(6)% in group 1 (p = 0.01), and to 26(5)% in group 3 (p = 0.02). Similar differences between the groups were observed for the increase in heart rate during acetylcholine infusions. In contrast, the responses to glyceryl trinitrate were similar in all groups. After infusions of L-nitro-arginine, the responses to acetylcholine were blunted.

CONCLUSIONS

Supplementation with vitamin E restored the otherwise reduced vascular response to acetylcholine in cholesterol fed rabbits. Analysis of photoplethysmographic pulse curves is a simple non-invasive method of evaluating arterial vasodilator effects. However, the nature of the measured dilator response needs to be characterised further.

Effect of cold pressor test and awareness of hypertension on platelet function in normotensive and hypertensive women

Plasma beta-thromboglobulin (beta-TG) concentration, reflecting platelet function in vivo, was compared in fertile women with untreated essential hypertension and age-matched normotensives, in two separate studies. In the first study, hypertensives and normotensives were aware of their blood pressure status. Blood was sampled through arterial and venous indwelling catheters, and no difference in beta-TG was found between the groups. Arterial beta-TG was significantly lower than venous concentration (p < or = 0.05). Cold pressor test increased arterial beta-TG significantly in both groups (p < 0.05). In the second study, both women and investigator were unaware of blood pressure status, and beta-TG concentration, platelet count, and mean platelet volume obtained by venipunctures were similar in the hypertensive and normotensive group. Thus, platelet function in vivo seems to be normal in fertile hypertensive women, in contrast to the platelet dysfunction previously reported in hypertensive men. In women, as in men, platelet release occurred during venous catheter blood sampling and during cold pressor test. However, at variance from men, platelet function was not influenced by awareness of blood pressure status in the hypertensive females.

[Guidelines for use of amiodarone (Cordarone). A potent anti-arrhythmic agent that may have problematic adverse effects]

The authors discuss the potent antiarrhythmic drug amiodarone, with emphasis on indications, efficacy and side effects. At present the drug can be prescribed only by specialists in internal medicine. In order to monitor the efficacy of the drug and any side effects the patient should preferably be evaluated every three to six months. Use of intravenous amiodarone in hospital is effective in many cases but, so far, documentation on this treatment is limited.

[The practical benefits of ambulatory continuous ECG recording]

The diagnostic yield from ambulatory continuous ECG recording (Holter ECG) has been evaluated retrospectively in 200 consecutive patients referred from an urban population of 250,000 for arrhythmia diagnosis or evaluation. About half of the patients were in hospital, the other half were ambulatory. In 20/200 (10%) the examination was obviously useful: indication for therapy was documented or arrhythmia and symptoms did not coincide. 53/200 (26.5%) possibly benefited, with qualitative or quantitative observations of clinical interest, and 127 (63.5%) probably did not benefit (no previously unknown findings of importance). Of the 85 patients referred for syncope, six obviously benefited and ten possibly benefited from the examination.

Heating and cooling of the nitroglycerin patch application area modify the plasma level of nitroglycerin

19 healthy volunteers wore a nitroglycerin patch releasing 10 mg per 24 h for 2 h. Subsequently, the skin area surrounding the patch was exposed to 15 min of local heating with an infrared bulb (Group A, n = 10), or local cooling with an ice-pack (Group B, n = 9). The patch was protected by an insulating shield (Styrofoam). After 10 min of heating, the median (Walsh) plasma nitroglycerin level increased from 3.1 to 7.6 nmol.l-1. Body temperature remained constant. After 15 min of cooling the median plasma level had dropped from 2.1 to 1.4 nmol.l-1. The results demonstrate that changes in skin temperature may cause extensive short-term changes in the bioavailability of nitroglycerin. Presumably, a subcutaneous or cutaneous reservoir builds up during transdermal treatment, and changes in regional cutaneous blood flow affect the rate of drainage from the reservoir into the systemic circulation.

The effect of transdermal nitroglycerin on exercise tolerance in relation to patch application time--a meta-analysis

Disagreeing results have been reported in the many studies on continuous treatment with nitroglycerin patches. The effects on exercise tolerance are partly studied at the end of a 24-hour application period, and partly examined only a few hours after patch renewal. The present meta-analysis estimates the overall efficacy of nitroglycerin patches in trials with and without concomitant antianginal therapy, and investigates if the treatment effect depends on the patch application time. A computed search (MEDLINE) identified 110 publications, of which 17 trials on nitrate patch monotherapy and six trials on combined therapy satisfied the inclusion criteria. Data on "exercise duration" and "ST-segment depression" were converted to a standardized treatment effect size d, and pooled to an overall treatment effect size d+. In tests 2-5 hours after patch renewal, moderate but significant effects of nitrate monotherapy were observed; d+ was 1.20 with regard to "ST-segment depression" and 0.39 with regard to "exercise duration" (both p < 0.0001). In contrast, 24 hours after patch application, the values for d+ were 0.09 (not significant) and 0.36 (p < 0.01), respectively. When adding the results from the six trials on combined therapy, d+ with regard to "exercise duration" was reduced to 0.28 (p < 0.0001) 2-5 hours after renewal and to 0.17 (p = 0.04) after 24 hours. Thus, the efficacy of continuous nitroglycerin patch treatment is moderate but evident during exercise tests 2-5 hours after patch renewal; however, it is reduced after 24 hours of patch application.

[Cooperation between regional and central hospitals--how to achieve the best results?]

The authors reviews a recent governmental analysis of cooperation between third-line university clinics and local and central hospitals. The hospitals are owned by the government (mainly by the counties), and the various Acts and regulation permit the central authorities to make decisions on all aspects of highly specialized medicine. The analysis concludes that a limited number of problems should be solved by decision of the central government, but only those where national concerns are involved. The counties within a health region should cooperate within a Regional Health Policy Board, to create plans for flow of patients through the health care system, specified for each field of medicine. When such plans have been approved by the Regional Health Policy Board, each county should be willing to accept them. In the event of local disagreement, the central government should decide.

[Highly specialized medicine. How to assign the tasks?]

Norway has four million inhabitants and five university hospitals, each serving one health region. The authors describe the work of a governmental medical committee, whose mandate is to advise on where to locate the various highly specialized medical services. Important questions have been the relationship between experience and quality, and the desire of each university clinic to be able to provide treatment within its own region for most health problems. Their reasons are concern about research and specialist training, and the preference of patients for treatment near to home. A list of proposed national and over-regional centers for certain treatments has been prepared on the basis of the experts' report and comments from all university clinics. These recommendations have provided a medical basis for later economic and political analyses prior to final decision by the Government. Norwegian legislation permits strong governmental regulation of the highly specialized health services.

The epinephrine-blood platelet connection with special reference to essential hypertension

About three decades ago it was shown by an aggregometer that epinephrine activated blood platelets, and it was proposed that platelets could be the link between stress and cardiovascular disease. During the past 10 years this hypothesis has been tested in clinical studies. It has been found that subjects with hypertension consistently have raised plasma catecholamine levels and in particular elevated epinephrine levels. Arterial but not venous epinephrine concentrations correlated with plasma concentrations of the platelet-release reaction marker beta-thromboglobulin (BTG). Plasma BTG is elevated in hypertensive patients, and psychological stress (i.e., hypertension labeling) stimulates plasma epinephrine and BTG. When a physiologic dose of epinephrine is infused into essential hypertensive patients, platelet counts, platelet size, and plasma BTG concentrations increase more than in normotensive subjects. Data suggest that there is a connection between psychological stress, plasma epinephrine levels, and platelet function, especially in patients with essential hypertension.

Transdermal nitrate therapy: bioavailability during exercise increases transiently after the daily change of patch

Ten volunteers carried a 10 mg 24 h -1 transdermal glyceryl trinitrate (GTN) patch for 24 h before moderate exercise. Plasma GTN-concentration increased significantly (P less than 0.05) by 19% to peak value at 15 min. Two hours after patch renewal repeat exercise increased GTN concentration by 56% (P less than 0.001). The two nitrate-concentration curves differed significantly (P less than 0.0001). Thus, change of patch augmented nitrate availability during exercise.

Increased arterial adrenaline is related to pain in uncomplicated myocardial infarction

Plasma levels of catecholamines, beta-thromboglobulin (BTG) and arginine vasopressin (AVP), and degree of pain were examined in 22 patients with suspected uncomplicated myocardial infarction within 24 h following onset of chest pain. Sixteen patients developed infarction with peak creatine phosphokinase at 1280 Ul-1 (range 293-3770 Ul-1). Fifteen healthy men served as controls (C). Arterial adrenaline levels were significantly higher in patients with pain (1.15 +/- 0.23 nmol l-1, n = 8, mean value +/- SEM) than in those without pain (0.60 +/- 0.10 nmol l-1, n = 14, P less than 0.05). Plasma catecholamines were moderately but significantly elevated in myocardial infarction; the concentration of arterial adrenaline was 0.83 +/- 0.14 nmol l-1 and that of arterial noradrenaline was 2.70 +/- 0.28 nmol l-1 compared with 0.44 +/- 0.04 nmol l-1 (P less than 0.025) and 1.47 +/- 0.05 nmol l-1 (P less than 0.0005), respectively, in C. One week later, plasma catecholamines had returned to baseline levels. Plasma BTG showed borderline elevation (1.0 +/- 0.1 pmol l-1) compared with C (0.6 +/- 0.1 pmol l-1, P = 0.04), and remained unchanged 1 week later. Plasma AVP was at baseline level. Uncomplicated myocardial infarction, regardless of size, was associated with only moderately increased sympathetic tone. Plasma adrenaline was related more to the degree of pain than to the presence of acute myocardial infarction. Arterial adrenaline may be a sensitive marker of sympatho-adrenal activity related to pain.

[Ischemic left ventricular failure. Main stem coronary stenosis treated with angioplasty]

We describe a patient with stenosis on the left main stem and severe impairment of the left ventricular function. Because of reversible myocardial ischaemia in a patient whose clinical situation prohibited surgery, angioplasty on the left main stem was performed, leading to considerable improvement of the ventricular function. Improvement was slow, however, probably due to "stunning" of the myocardium. We underline the importance of early angiography in patients when it is suspected that a larger part of the myocardium is affected by severe, reversible ischaemia.

[Drug therapy of acute myocardial infarction and unstable coronary syndrome]

Questionnaires were sent to 61 Norwegian hospitals treating acute coronary syndromes, and 90% replied. Thrombolytic drug treatment is now the routine when the history of chest pain is short and ischemia appears in ECG. Use of glyceryl trinitrate and beta blocking drugs varies considerably, as does the use of oral anticoagulants and platelet inhibitors. Practice also varies in unstable angina. However, a combination of aspirin, intravenous nitrate, and betablockers is common. Several treatment regimens have an uncertain scientific foundation. The varying practice reflects international scientific debate.

Awareness of high blood pressure stimulates platelet release reaction

The present study aimed at testing the hypothesis of a link between mental stress and blood platelet function. Twenty-nine 19-year-old men were recruited from the 98th percentile of mean blood pressure (116 mmHg) at a routine medical screening. They were not informed about their elevated blood pressures at the time of the screening. One year later they were randomized into two groups. Group 1 (n = 16) was exposed to mental stress by a letter informing them about their high blood pressure, while group 2 (n = 13) was sent a neutral letter. At an examination 2 weeks later, heart rate (p less than 0.05) and plasma adrenaline (p less than 0.05) responses to a cold pressor test were exaggerated in the informed group. The plasma beta-thromboglobulin (beta TG) concentration was elevated in the informed group (p less than 0.05) as was mean blood pressure (p less than 0.05). beta TG correlated positively with hematocrit (r = 0.59, p less than 0.005) and mean blood pressure (r = 0.43, p less than 0.05), and negatively with plasma HDL (r = -0.61, p = 0.001). The study shows that awareness of hypertension induces a hyperadrenergic state which is associated with the platelet release reaction. Under these circumstances platelet release seems to be correlated to established coronary heart disease risk factors.

[Vasospastic angina pectoris]

The authors discuss the pathogenesis and treatment of variant angina pectoris, and illustrate the condition by describing nine cases. Alertness for the presence of coronary spasms is recommended, and also the more frequent use of provocative diagnostic tests.

Effect of dopamine and dopamine-antagonist infusion on blood platelet count, size and release reaction in hypertensive and normotensive subjects

To examine the effect of dopamine on in vivo platelet function and a possible platelet contribution to the clearance of dopamine we measured platelet count, platelet size and plasma concentration of the platelet specific protein beta-thromboglobulin (BTG) in groups of 40 year old untreated hypertensive and normotensive men. One hypertensive (n = 10) and one normotensive (n = 10) group received dopamine infusion at doses from 0.5 to 2.0 micrograms/kg/min which increased plasma dopamine 100-fold from baseline. Two other groups of hypertensive (n = 10) and normotensive (n = 11) subjects received 10 mg of the dopamine antagonist metoclopramide intravenously, upon which serum prolactin concentration increased 10-fold. No significant effect on platelet function in any group was observed during these interventions. Platelet phenol-sulphotransferase may contribute to dopamine conjugation. However, the selected platelet parameters correlated only weakly with dopamine kinetics during the infusion. Neither dopamine nor a dopamine antagonist altered the selected platelet parameters, nor did these parameters influence the clearance of dopamine during a short-lasting pharmacological infusion.

Hyper-responsiveness to low-dose epinephrine infusion in mild essential hypertension

The present study was undertaken to evaluate the effects of intravenous infusion of small amounts of epinephrine on haemodynamics, renal electrolyte excretion and blood platelets in essential hypertension. Arterial plasma epinephrine concentrations were increased during the infusion to approximately 2.5 nmol/l both in a group of 40-year-old men with untreated mild essential hypertension (blood pressure 154 +/- 3/100 +/- 3 mmHg, n = 12) and in a group of age-matched male controls (124 +/- 3/78 +/- 2 mmHg, n = 11). In the hypertensive group only, mean blood pressure decreased, forearm blood flow increased, forearm vascular resistance decreased (P less than 0.001 for all) and the urinary excretion of sodium and potassium increased (P less than 0.01 for both). The hypertensive group also responded with an increase in plasma beta-thromboglobulin (P less than 0.05), blood platelet size (P less than 0.05) and a higher increase in platelet counts than in the normotensive group (P less than 0.05). Thus, in several ways the hypertensive patients showed a hyper-responsiveness to amounts of epinephrine which corresponds well to the plasma concentration achieved during psychological and physical activity.

Decreased platelet-free dopamine and unchanged noradrenaline and adrenaline in essential hypertension

The content of free-catecholamines in blood platelets is much higher than in plasma and platelet catecholamines must be taken up from plasma, since platelets lack the enzymes for catecholamine synthesis. There is some evidence that platelet catecholamine content under certain circumstances may be an integrated measure of plasma catecholamine concentrations over time. Platelet-free catecholamines were therefore assayed in 18 untreated patients with essential hypertension and in 16 normotensive control subjects. Mean platelet-free dopamine in the hypertensive group was 3.7 +/- 0.4 pg/mg platelet weight, i.e. significantly less than the 6.5 +/- 0.9 pg/mg found in the normotensive (p less than 0.005). Platelet contents of noradrenaline and adrenaline did not differ. Decreased platelet-free dopamine and unchanged platelet noradrenaline and adrenaline persisted after adjustment for increased body weight in the hypertensive group. Although the reasons for decreased platelet-free dopamine in the hypertensive group remain unknown, this finding may add to previous result showing facilitated release of granular contents from blood platelets in patients with essential hypertension. Our data do not support platelet levels of free-catecholamines to be a marker of increased sympathetic tone in essential hypertension.

Sodium depletion increases platelet and plasma catecholamines in hypertensive men

The catecholamine content in blood platelets is considerably higher than that in plasma, and platelet catecholamines must be taken up from plasma, since blood platelets lack enzymes for catecholamine synthesis. However, it is unknown whether platelets take up and store catecholamines during physiological in vivo increments in plasma catecholamines. Previously untreated 50-year-old men (n = 17) with mild to moderate essential hypertension were given a low sodium diet for 2 weeks. Urinary excretion of sodium decreased from 201 +/- 11 (SE) to 24 +/- 5 and 19 +/- 4 mmol/24 hr after 1 and 2 weeks, respectively. During the first week, the blood platelet concentration of norepinephrine increased from 27.2 +/- 2.9 to 39.6 +/- 4.7 pg/mg (p less than 0.005) and venous plasma norepinephrine increased from 3.7 +/- 0.4 to 5.6 +/- 0.5 pg/ml (p less than 0.005), and venous plasma dopamine increased from 26 +/- 4 to 41 +/- 5 pg/ml (p less than 0.05). During the second week, both plasma and platelet norepinephrine and dopamine remained elevated. Platelet epinephrine showed a small increase from baseline to the second week (p less than 0.05), but no concomitant increase in plasma epinephrine occurred. Thus, sodium depletion increases both platelet and plasma catecholamines and blood platelets may take up catecholamines in vivo. Platelet catecholamine content may be an integrated measure of plasma catecholamine concentrations during variations caused by sodium depletion.

Does increased platelet release normalize during anti-hypertensive treatment?

Blood platelet function was evaluated in 10 men, all 50 years old, with untreated, mild hypertension. Each patient was examined four times: At the beginning of the study, after 5 weeks on placebo treatment, after the following 5 weeks on propranolol 160 mg daily, and finally after a second period of 5 weeks on placebo. At baseline the plasma level of the platelet release product beta-thromboglobulin (BTG) was 41.6 (30.5-57.0) micrograms/l (median and 95% confidence interval). During the first placebo period BTG was normalized to 21.0 (14.1-25.9) micrograms/l. While systolic blood pressure and heart rate fell during beta-adrenergic receptor blockade, BTG remained unchanged throughout the rest of the observation periods. Platelet size increased significantly during treatment with beta-blocker. The present study indicates that the normalization of elevated platelet function which previously has been reported to occur during anti-hypertensive drug therapy, may be explained by patient adaptation to the blood sampling procedure.

Increased platelet size and release reaction in essential hypertension

Basal platelet function was measured in 35 40-year-old men with untreated mild essential hypertension and compared with 44 age-matched normotensive men. The groups differed significantly with respect to platelet size in venous blood (hypertensive, 7.46 +/- 0.10 X 10(-15) l versus normotensive, 7.11 +/- 0.09 X 10(-15) l; P = 0.01) and arterial concentration of the platelet-specific protein beta-thromboglobulin (hypertensive, 1.11 +/- 0.23 nmol/l versus normotensive, 0.59 +/- 0.04 nmol/l; P = 0.02). The normotensive subjects had significantly higher beta-thromboglobulin (BTG) in venous than in arterial blood (P less than 0.01). The hypertensive men showed no such difference. In contrast to the normotensive subjects, the hypertensive group had reduced arterial compared with venous platelet count (P less than 0.01). This may reflect an increased liability in the hypertensive subjects to lose platelets through adherence to the cannula during arterial blood sampling. The above findings point to increased platelet activity in essential hypertension, particularly in arterial blood.

Blood donor selection can prevent cytomegalovirus infection after open heart surgery

Thirty-four patients without IgG antibodies against cytomegalovirus (CMV) prior to open heart surgery were studied. The patients were randomized to receive blood either from unselected donors, or from donors without detectable CMV antibodies. Fresh whole blood was mainly used. Eleven patients received CMV seronegative blood only. All had an uneventful convalescence period and remained seronegative. Ten of the 23 patients who received blood from unselected donors had typical CMV disease with the onset of symptoms in the third or fourth postoperative week, and fever lasting for two to three weeks. They all had liver enzyme release and later seroconversion against CMV. Four patients were hospitalized during this period. The incidence of symptomatic CMV infection after open heart surgery was higher than usually reported among the CMV seronegative patients. Selection of blood donors who lack antibodies against CMV may be an adequate protective measure. Avoidance of fresh blood and reduced use of blood products are presumably also of importance.

Does Increased Platelet Release Normalize During Anti-Hypertensive Treatment?

Blood platelet function was evaluated in 10 men, all 50 years old, with untreated, mild hypertension. Each patient was examined four times: At the beginning of the study, after 5 weeks on placebo treatment, after the following 5 weeks on propranolol 160 mg daily, and finally after a second period of 5 weeks on placebo. At baseline the plasma level of the platelet release product (β-thromboglobulin (BTG) was 41.6 (30.5-57.0) μg/l (median and 95% confidence interval). During the first placebo period BTG was normalized to 21.0 (14.1-25.9) μg/l. While systolic blood pressure and heart rate fell during β-adrenergic receptor blockade, BTG remained unchanged throughout the rest of the observation periods. Platelet size increased significantly during treatment with β-blocker. The present study indicates that the normalization of elevated platelet function which previously has been reported to occur during anti-hypertensive drug therapy, may be explained by patient adaptation to the blood sampling procedure.

Increased platelet release reaction in 50-year-old men with essential hypertension: correlation with atherogenic cholesterol fractions

Beta-thromboglobulin (BTG) is a platelet-specific release product. Plasma BTG was significantly increased (p less than 0.01) in 50-year-old, untreated essential hypertensive men (1.22 +/- 0.13 nmol/L, n = 39, mean +/- SE) compared to 50-year-old, healthy normotensive control men (0.82 +/- 0.07 nmol/L, n = 31). Plasma BTG in the hypertensive group correlated significantly with the total serum cholesterol concentration (r = 0.47, p less than 0.01) and with the atherogenic cholesterol fractions low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) cholesterol (r = 0.50, p less than 0.01). In the normotensive group, no significant correlation was observed between plasma BTG and total serum cholesterol (r = 0.14) or between plasma BTG and LDL + VLDL cholesterol (r = 0.08). Neither was any significant correlation found between plasma BTG and serum high-density lipoprotein (HDL) cholesterol or total triglycerides in either group. Thus, middle-aged men with untreated essential hypertension have an increased blood platelet release reaction related to their concentrations of atherogenic blood lipids. This relationship may be of pathogenetic importance for atherogenesis in hypertension.

Increased plasma noradrenaline during severe sodium restriction does not stimulate platelet release in essential hypertension

Seventeen 50-year old hypertensive men, previously untreated with blood pressure 157 +/- 4/110 +/- 2 mmHg (means +/- SE) were given a low sodium diet for 2 weeks. During the second week, the diet was supplemented with potassium. The urinary Na+/K+ excretion ratio changed from 2:1 to 1:4 and 1:11, respectively. Sympathetic noradrenergic tone increased considerably during the first week. Thus, venous plasma noradrenaline increased from 254 +/- 22 to 347 +/- 28 pg/ml (p less than 0.001) and arterial concentration from 253 +/- 36 to 317 +/- 42 pg/ml (n = 10, p less than 0.001). No significant change was observed in sympathetic adrenal tone as reflected by normal plasma adrenaline in venous (42 +/- 5 vs 43 +/- 6 pg/ml, ns) or arterial blood (71 +/- 10 vs 82 +/- 15 pg/ml, n = 10, ns) or in venous plasma concentration of the blood platelet release product beta-thromboglobulin (BTG) (50 +/- 8 vs 43 +/- 5 ng/ml, ns). During the second week sympathetic noradrenergic tone remained highly significantly elevated compared to baseline but still no change in plasma adrenaline or plasma BTG was found. Thus, whereas sodium depletion did increase plasma noradrenaline concentration markedly in these hypertensive men, no change in adrenaline concentration was observed, and blood platelet release reaction was unchanged. Plasma noradrenaline within the physiological concentration range does not seem to serve as a regulator of in vivo platelet function.

Increased uptake of transdermal glyceryl trinitrate during physical exercise and during high ambient temperature

In a study of GTN absorption during exercise and high ambient temperature, 12 healthy volunteers carried 10 mg glyceryl trinitrate (GTN, nitroglycerin) transdermal patches for 6 hours during each of 3 days. During a control day the mean plasma GTN concentration ranged from 1.0 nmol/L (SD +/- 0.8 nmol/L) to 1.5 nmol/L (SD +/- 1.0 nmol/L), whereas during a bicycle ergometer day mean GTN concentration was increased to 3.1 nmol/L (SD +/- 1.7 nmol/L, p less than 0.001). During a sauna day volunteers stayed for 20 minutes in a sauna, and mean GTN concentration in plasma rose to 7.3 nmol/L (SD +/- 1.7 nmol/L, p less than 0.001). Systolic blood pressure increased during exercise (p less than 0.01) but decreased significantly in the sauna (p less than 0.01). Headache was noted frequently (9 of 12 subjects) and dizziness by a few (3 of 12). The demonstrated increased transdermal absorption in our study may infer an increased effect during workload. Whereas the increase in transdermally absorbed GTN may be beneficial to the exercising angina patient, increased effects of GTN may be undesirable in hot surroundings. A study on angina patients is justified to assess whether this phenomenon bears clinical relevance.

Enhanced platelet release reaction related to arterial plasma adrenaline and blood pressure in pre-eclampsia

The platelet release product beta-thromboglobulin (BTG) in venous plasma, and arterial and venous catecholamines were measured in 13 severe pre-eclamptic and 13 normotensive pregnant women. In the pre-eclamptic group, BTG was significantly higher and the platelet count significantly lower than in the normotensive pregnant group. In the pre-eclamptic group, arterial concentrations were significantly higher for adrenaline, noradrenaline and dopamine, whereas in venous plasma only adrenaline and dopamine were higher. Significant positive correlations appeared in the pre-eclamptic patients between venous BTG and arterial adrenaline (r = 0.82), arterial noradrenaline (r = 0.76) and venous adrenaline (r = 0.55). In the pre-eclamptic group, BTG also highly correlated with systolic (r = 0.84) and diastolic blood pressure (r = 0.77) and heart rate (r = 0.67). These findings indicate that sympathetic nervous tone, as measured by arterial and venous plasma catecholamines, is a good predictor of in-vivo blood platelet activation. In pre-eclampsia, increased sympathetic tone may play a key role in platelet activation and consumption and thus in the activation of the coagulation system.

Increased Plasma Noradrenaline During Severe Sodium Restriction Does Not Stimulate Platelet Release in Essential Hypertension

Seventeen 50-year old hypertensive men, previously untreated with blood pressure 157 ± 4/110 ± 2 mmHg (means ± SE) were given a low sodium diet for 2 weeks. During the second week, the diet was supplemented with potassium. The urinary Na+/K+ excretion ratio changed from 2:1 to 1:4 and 1:11, respectively.

Sympathetic noradrenergic tone increased considerably during the first week. Thus, venous plasma noradrenaline increased from 254 ± 22 to 347 ± 28 pg/ml (p <0.001) and arterial concentration from 253 ± 36 to 317 ± 42 pg/ml (n = 10, p <0.001). No significant change was observed in sympathetic adrenal tone as reflected by normal plasma adrenaline in venous (42 ± 5 vs 43 ± 6 pg/ml, ns) or arterial blood (71 ± 10 vs 82 ± 15 pg/ml, n = 10, ns) or in venous plasma concentration of the blood platelet release product beta-thromboglobulin (BTG) (50 ± 8 vs 43 ± 5 ng/ml, ns). During the second week sympathetic noradrenergic tone remained highly significantly elevated compared to baseline but still no change in plasma adrenaline or plasma BTG was found.

Thus, whereas sodium depletion did increase plasma noradrenaline concentration markedly in these hypertensive men, no change in adrenaline concentration was observed, and blood platelet release reaction was unchanged. Plasma noradrenaline within the physiological concentration range does not seem to serve as a regulator of in vivo platelet function.

Increased arterial adrenaline is highly correlated to blood pressure and in vivo platelet function in pre-eclampsia

Compared with normotensive pregnant women (n = 13), patients with severe pre-eclampsia (n = 13) had increased arterial plasma adrenaline (P < 0.001), peripheral venous adrenaline (P < 0.01), arterio-venous differences of adrenaline (P < 0.001) and venous concentration of the platelet release product beta-thromboglobulin (P < 0.001). In the pre-eclamptic group, arterial adrenaline correlated with mean blood pressure (r = 0.90, P < 0.001), heart rate (r = 0.78, P < 0.01) and beta-thromboglobulin (r = 0.82, P < 0.001), while in the normotensives adrenaline correlated only with beta-thromboglobulin (r = 0.76, P < 0.01). According to these results, sympathetic adrenal tone is increased in pre-eclampsia and may play a role in the pathogenesis of high blood pressure and platelet activation in this disease.