Postexercise alpha-adrenergic receptor hyporesponsiveness in hypertensive rats is due to nitric oxide

Post-exercise hypotension in male spontaneously hypertensive rats: The issue of calculation method

In spontaneously hypertensive rats, exercise can lead to a post-exercise decrease in blood pressure, named post-exercise hypotension (PEH). This can be following physical training but also after a single bout of mild to moderate exercise when measured with tail-cuff or externalized catheter methods. Our aim was to assess the PEH obtained with different calculation methods and to compare the magnitude of this effect induced by a moderate-intensity continuous exercise or a high-intensity intermittent exercise. Thirteen 16-week-old male spontaneously hypertensive rats performed two types of aerobic exercise (continuous or intermittent) on a treadmill. Arterial pressure was recorded by telemetry for 24 h which was started 3 h before physical exercise. Based on the literature, PEH was first evaluated with two different baseline values, and then with three different approaches. We observed that the identification of PEH depended on the method used to measure the rest value, and that its amplitude was also influenced by the calculation approach and the type of exercise performed. Hence, the calculation method and the amplitude of the detected PEH can significantly influence their physiological and pathophysiological inferences.

Effects of acute moderate-intensity exercise at different duration on blood pressure and endothelial function in young male patients with stage 1 hypertension

PURPOSE

The studies regarding the effects of exercise duration on blood pressure have reported inconsistent and conflicting results. Nitric oxide (NO) is a well-known vasodilator released by endothelial cells, and endothelial microparticles (EMPs) are membranous vesicles released into the circulation from activated or apoptotic endothelial cells, both of whose level can reflect the endothelial function. But few studies have been done to explore the effect of exercise duration on blood pressure and endothelial function, especially, the EMPs response to exercise in young male patients with hypertension. This study aimed to investigate the blood pressure response during moderate-intensity exercise performed in different durations and the acute effects on post-exercise hypotension and endothelial function in hypertensive patients.

METHODS

Eighteen young male hypertensive patients who did not take antihypertensive drugs were recruited in this study. They randomly performed twice exercises on a cycle ergometer at a moderate intensity of 40%-50% of their HR reserve; one was 20 min (E20 session), the other one was 40 min (E40 session); there was 1-week break between the two exercises. Blood pressure was monitored by the YUWELL blood pressure monitor at rest, every 5 min during exercise, and 3 and 6 min post-exercise. The level of NO (nitrate/nitrite reduction) and EMPs (flow cytometry) in plasma were detected before and immediately following exercise. CD31⁺/CD42b^- events were classified as EMPs and events per microliter plasma were calculated. This study was approved by the Beijing Sport University Institutional Review Board (protocol number 2019087 H).

RESULTS

Mean age of patients was 34.8 ± 3.5 yrs, and BMI was 27.6 ± 2.7 kg/m². Systolic blood pressure (SBP) in the two sessions increased significantly during exercise. The SBP in the E20 session increased by 37 mmHg (P < .01) at 5 min during exercise and remained stable afterward. In the E40 session, the SBP increased by 35 mmHg (P < .01) at 5 min during exercise and was stable at 5 through 25 min, decreased by 8 mmHg at 25 through 35 min during exercise, and then stabilized (P < .01). There was no obvious change of diastolic blood pressure (DBP) in the two sessions during exercise. In the E20 session, SBP at 6 min following exercise was no different from the rest; in the E40 session, SBP at 6 min following exercise was 14 mmHg lower than at the rest (P < .01). DBP in the E20 session was the same as rest at 3 min following exercise and decreased by 4 mmHg at 6 min following exercise compared with the rest (P < .05), while DBP in the E40 session decreased by 3 mmHg at 3 min following exercise compared with the rest (P < .05). The plasma NO levels of E20 and E40 increased significantly following exercise (P < .01 for both). There was no difference in plasma NO level between the two sessions pre- and post-exercise, but the increased magnitude of NO level in E40 was greater than that in E20 (24.47% vs. 9.24%, P < .01). The plasma EMPs level of E20 and E40 decreased significantly following exercise (P < .01 for both). There was no difference in plasma EMPs level between the two sessions pre- and post-exercise, but the decreased magnitude of EMPs level in E40 was greater than that in E20 (15.66% vs. 8.00%, P < .01).

CONCLUSION

There is no exaggerated blood pressure response to 20-min and 40-min acute moderate-intensity exercise in young hypertensive men with no antihypertensive drugs. Both 20-min and 40-min acute moderate exercise can reduce the rest blood pressure, and improve endothelial function by increasing NO and decreasing EMPs in young male patients with hypertension, and the effects of 40-min exercise on lowering SBP and improving endothelial function are better than that of 20-min.

Whole Red Grape Juice Reduces Blood Pressure at Rest and Increases Post-exercise Hypotension

OBJECTIVE

The objective of this study was to evaluate the effect of whole red grape juice (juice) on blood pressure (BP) at rest and on the magnitude of post-exercise hypotension (PEH).

METHODS

This double-blind, randomized controlled study was performed with 26 individuals with hypertension (40 to 59 years old) who were divided into experimental (n = 14) and control (n = 12) groups. Subsequently, the experimental group was subdivided according to the initial BP values. The subjects performed 2 sessions of aerobic exercise on a treadmill (60 minutes, 60%-85% maximum heart rate), separated by a 28-day period of supplementation with a daily dose of juice (150 ml for men and 100 ml for women) or a control drink. BP was measured before, during, and immediately after each exercise session as well as every 10 minutes during the 60-minute post-exercise recovery period.

RESULTS

The BP at rest did not change in the experimental group, but when this group was subdivided by initial BP, the subjects with controlled initial BP (EGCP) achieved a significant reduction (133.3 ± 5.6 to 114.6 ± 12.2 mmHg, p = 0.02); in contrast, the experimental group with borderline hypertensive BP values (EGBP) did not. Intervention with juice did not modify PEH in the experimental group, but when this group was divided as a function of the initial BP, PEH was potentiated at some times in EGCP.

CONCLUSIONS

We conclude that juice promotes a reduction in BP at rest and is also capable of improving PEH in individuals with hypertension, but these effects are dependent on the initial BP values.

A Single Resistance Exercise Session Improves Aortic Endothelial Function in Hypertensive Rats

BACKGROUND

Physical exercise is an important tool for the improvement of endothelial function.

OBJECTIVE

To assess the effects of acute dynamic resistance exercise on the endothelial function of spontaneously hypertensive rats (SHR).

METHODS

Ten minutes after exercise, the aorta was removed to evaluate the expression of endothelial nitric oxide synthase (eNOS), phosphorylated endothelial nitric oxide synthase (p-eNOS1177) and inducible nitric oxide synthase (iNOS) and to generate concentration-response curves to acetylcholine (ACh) and to phenylephrine (PHE). The PHE protocol was also performed with damaged endothelium and before and after NG-nitro-L-arginine methyl ester (L-NAME) and indomethacin administration. The maximal response (Emax) and the sensitivity (EC50) to these drugs were evaluated.

RESULTS

ACh-induced relaxation increased in the aortic rings of exercised (Ex) rats (Emax= -80 ± 4.6%, p < 0.05) when compared to those of controls (Ct) (Emax = -50 ± 6.8%). The Emax to PHE was decreased following exercise conditions (95 ± 7.9%, p < 0.05) when compared to control conditions (120 ± 4.2%). This response was abolished after L-NAME administration or endothelial damage. In the presence of indomethacin, the aortic rings' reactivity to PHE was decreased in both groups (EC50= Ex -5.9 ± 0.14 vs. Ct -6.6 ± 0.33 log µM, p < 0.05 / Emax = Ex 9.5 ± 2.9 vs. Ct 17 ± 6.2%, p < 0.05). Exercise did not alter the expression of eNOS and iNOS, but increased the level of p-eNOS.

CONCLUSION

A single resistance exercise session improves endothelial function in hypertensive rats. This response seems to be mediated by increased NO production through eNOS activation.

Obesity-Induced Hypertension Develops in Young Rats Independently of the Renin-Angiotensin-Aldosterone System

A correlation exists between obesity and hypertension. In the currently available models of diet-induced obesity, the treatment of rats with a high fat (HF) diet does not begin until adulthood. Our aim was to develop and characterize a model of pre-pubescent obesity-induced hypertension. Male Sprague-Dawley rats were fed a HF diet (35% fat) for 10 weeks, beginning at age 3 weeks. Blood pressure was measured by tail-cuff, and a terminal blood sample was obtained to measure fasting blood glucose, insulin, plasma renin, aldosterone, thiobarbitutic acid reactive substances (TBARS), and free 8-isoprostanes levels. The vascular reactivity in the aorta was assessed using a myograph. Blood pressure was increased in rats fed the HF diet (HF, 161 ± 2 mm Hg vs. control, 137 ± 2 mm Hg, P < 0.05). Blood glucose (HF, 155 ± 4 mg/dL vs. control, 123 ± 5 mg/dL, P < 0.05), insulin (HF, 232 ± 63 pM vs. control, 60 ± 11 pM, P < 0.05), TBARS (expressed as nM of malondialdehyde [MDA]/ml [HF, 1.8 ± 0.37 nM MDA/ml vs. control 1.05 ± 0.09 nM MDA/ml, P < 0.05]), and free 8-isoprostanes (HF, 229 ± 68 pg/ml vs. control, 112 ± 9 pg/ml, P < 0.05) levels were elevated in the HF diet group. Interestingly, plasma renin and aldosterone levels were not different between the groups. The maximum vasoconstriction to phenylephrine (10−4 M) was increased in the HF diet group (HF, 26.1 ± 1.5 mN vs. control 22.3 ± 1.2 mN, P < 0.05). In conclusion, pre-pubescent rats become hypertensive and have increased oxidative stress and enhanced vasoconstriction when fed a HF diet. Surprisingly, this occurs without the increase in renin or aldosterone levels seen in the adult models of diet-induced obesity.

A single resistance exercise session improves myocardial contractility in spontaneously hypertensive rats

Resistance training evokes myocardial adaptation; however, the effects of a single resistance exercise session on cardiac performance are poorly understood or investigated. This study aimed to investigate the effects of a single resistance exercise session on the myocardial contractility of spontaneously hypertensive rats (SHRs). Male 3-month-old SHRs were divided into two groups: control (Ct) and exercise (Ex). Control animals were submitted to sham exercise. Blood pressure was measured in conscious rats before the exercise session to confirm the presence of arterial hypertension. Ten minutes after the exercise session, the animals were anesthetized and killed, and the hearts were removed. Cardiac contractility was evaluated in the whole heart by the Langendorff technique and by isometric contractions of isolated left ventricular papillary muscles. SERCA2a, phospholamban (PLB), and phosphorylated PLB expression were investigated by Western blot. Exercise increased force development of isolated papillary muscles (Ex=1.0±0.1 g/mg vs Ct=0.63±0.2 g/mg, P<0.05). Post-rest contraction was greater in the exercised animals (Ex=4.1±0.4% vs Ct=1.7±0.2%, P<0.05). Papillary muscles of exercised animals developed greater force under increasing isoproterenol concentrations (P<0.05). In the isolated heart, exercise increased left ventricular isovolumetric systolic pressure (LVISP; Δ +39 mmHg; P<0.05) from baseline conditions. Hearts from the exercised rats presented a greater response to increasing diastolic pressure. Positive inotropic intervention to calcium and isoproterenol resulted in greater LVISP in exercised animals (P<0.05). The results demonstrated that a single resistance exercise session improved myocardial contractility in SHRs.

Neurovascular control following small muscle-mass exercise in humans

Sustained postexercise vasodilation, which may be mediated at both a neural and vascular level, is seen in previously active skeletal muscle vascular beds following both large and small muscle-mass exercise. Blunted sympathetic vascular transduction and a downward resetting of the arterial baroreflex contribute to this vasodilation after cycling (large muscle-mass exercise), but it is unknown if these responses also contribute to sustained vasodilation following small muscle-mass exercise. This study aimed to determine if baroreflex sensitivity is altered, the baroreflex is reset, or if sympathetic vascular transduction is blunted following small muscle-mass exercise. Eleven healthy, college-aged subjects (five males, six females) completed one-leg dynamic knee-extension exercise for 1 h at 60% of peak power output. While cardiovagal baroreflex sensitivity was increased ∼23% postexercise relative to preexercise (P < 0.05), vascular and integrated baroreflex sensitivity were not altered following exercise (P = 0.31 and P = 0.48). The baroreflex did not exhibit resetting (P > 0.69), and there was no evidence of changes in vascular transduction following exercise (P = 0.73). In conclusion, and in contrast to large muscle-mass exercise, it appears that small muscle-mass exercise produces a sustained postexercise vasodilation that is largely independent of central changes in the baroreflex.

Neurohistological and behavioral changes following the four-vessel occlusion/internal carotid artery model of chronic cerebral hypoperfusion: comparison between normotensive and spontaneously hypertensive rats

Chronic cerebral hypoperfusion (CCH) may be a prodromal feature of aging-related dementias, and chronic hypertension is a major risk factor. We used a permanent, four-vessel occlusion/internal carotid artery (4-VO/ICA) model to evaluate the cognitive and neurohistological outcomes of CCH in both young and middle-aged rats. Young rats are asymptomatic after permanent 4-VO/ICA, and we tested the hypothesis that chronic hypertension aggravates the outcomes of CCH. Young normotensive rats (NTRs) and young spontaneously hypertensive rats (SHRs) were first subjected to 4-VO/ICA and then examined for hippocampal and cortical neurodegeneration 7, 15, and 30 days later. In a second experiment, both NTRs and SHRs were then trained in a modified, non-food-rewarded aversive radial maze (AvRM) task until acquiring asymptotic performance and then subjected to 4-VO/ICA. Thirty days later, they were assessed for memory retention of the previously acquired cognition. In a third, post hoc experiment, middle-aged NTRs were trained in the AvRM, subjected to 4-VO/ICA, and tested for memory retention 30 days later. Compared with NTRs, both SHRs and middle-aged NRTs had severe hippocampal and cortical damage, but they did not differ from each other, regardless of the chronicity of 4-VO/ICA. In contrast, NTRs were behaviorally asymptomatic, and retrograde memory performance was persistently impaired in SHRs. This amnesic effect in the SHR group was very similar to the middle-aged NTR group. These findings suggest that chronic hypertension deteriorates the capacity of the brain to adaptively respond to CCH. This influence of hypertension may parallel the effect of aging.

Remodeling of elastic layer of aortic artery after training by swimming in spontaneously hypertensive rats

Hypertension is a major risk factor for cardiovascular diseases, in which the elastic properties of arteries are subjected to high pressure levels, and networks of elastic fibers may develop cleft longitudinal, transverse, breaks and fragmentation, and such structural changes (fibrosis and degradation of elastin) may lead to a decrease in the elasticity of the artery. The descending thoracic aortas of normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHRs) subjected to physical training through swimming or those of sedentary rats were prepared with hematoxylin-eosin and Verhoff to assess the artery medial. The images were captured with a videocamera coupled to an ordinary light microscope and the images were analyzed with the same program. SHRs showed a larger area of the medial layer of the thoracic aorta (F = 25,764, P < 0.001), and it was observed that rats submitted to physical training through swimming showed a larger area of the thoracic aorta (t = 3.206, P = 0.011). There was a higher percentage of elastic trained (F = 6.536, P = 0.019). To conclude, this study aimed to determine the elastic component of the aortic artery in animals that underwent exercise when compared with those that did not perform the activity, and analyze the relationship between the area of the aortic wall in trained and sedentary animals. The principal conclusion is that the rigidity of the aorta is not increased in SHRs subjected to physical training compared with that of trained WKY animals; however, when sedentary SHRs were analyzed there was a decrease in the elasticcomponent, which can characterize the aortic arterial stiffness in SHRs.

Acute resistance exercise reduces blood pressure and vascular reactivity, and increases endothelium-dependent relaxation in spontaneously hypertensive rats

The aim of the present study was to assess the effects of acute dynamic resistance exercise on resting blood pressure (BP) and on endothelial function of vascular bed of spontaneously hypertensive rats. Hemodynamic measurements were performed before and after acute dynamic resistance exercise in conscious animals. After exercise, the tail artery was cannulated for mean perfusion pressure with constant flow measurement and for performing concentration-response curves to acetylcholine (ACh) and sodium nitroprusside (SNP) and dose-response curves to phenylephrine (PHE). PHE protocol was also repeated with damaged endothelium and after L-NAME and indomethacin perfusion on the tail. The maximal response (E(max)) and sensitivity (pD(2)) were evaluated to these drugs. Exercise reduced resting systolic and diastolic BP (Delta -79 +/- 1.8; -23 +/- 2.3 mmHg, respectively; P < 0.05). ACh-induced relaxation increased in the exercise group (pD(2) = 9.8 +/- 0.06, P < 0.05) when compared with control rats (pD(2) = 8.7 +/- 0.1). The E(max) to PHE with intact endothelium decreased following exercise condition (439 +/- 18 mmHg, P < 0.05) when compared with control rats (276 +/- 22 mmHg). This response was abolished after L-NAME and indomethacin administration. After damage of the endothelium, PHE responses were not significantly different between the groups; however, E(max) and pD(2) increased when compared with responses obtained with intact endothelium. The results demonstrated that acute dynamic resistance exercise decreased resting BP and reactivity to PHE and increased endothelium-dependent relaxation. Nitric oxide and vasodilators prostanoids appear to be involved in post-exercise endothelial and pressor responses.

Hipotensão pós-exercício aeróbio: uma revisão sistemática

Diversos estudos investigaram os efeitos hipotensores após uma sessão de exercício aeróbio em humanos. No entanto, vários aspectos permanecem obscuros em relação à hipotensão pós-exercício (HPE), uma vez que diversas variáveis podem influenciar a resposta hipotensora, como intensidade, duração, tipo de exercício, estado clínico, faixa etária, etnia, sexo e estado de treinamento. Nesse sentido, o objetivo do presente estudo foi revisar sistematicamente a literatura, relacionando as principais variáveis da prescrição de uma sessão de exercício aeróbio e a HPE, assim como apresentar os possíveis mecanismos envolvidos. Foram encontrados 55 estudos que abrangeram a temática HPE e exercício aeróbio em humanos. A ocorrência da HPE está bem estabelecida na literatura, já que vários estudos identificaram reduções da pressão arterial em normotensos e hipertensos. Porém, os possíveis moduladores das respostas hipotensoras, como intensidade e duração da sessão de exercício, ainda são contraditórios. Em relação ao tipo de exercício, porém, existem indicativos de que os realizados de forma intermitente e que utilizam maior massa muscular podem acarretar maior HPE. Além disso, hipertensos devem apresentar maior magnitude e duração da HPE. Contudo, existem lacunas em relação aos diversos mecanismos fisiológicos envolvidos, que parecem ser diferentes entre normotensos e hipertensos.

Endothelial nitric oxide synthase activation contributes to post-exercise hypotension in spontaneously hypertensive rats

We investigated the role that endothelial nitric oxide synthase plays in post-exercise hypotension in spontaneously hypertensive rats. To accomplish this, rats were subjected to a single bout of dynamic exercise on a treadmill at 15 m/min for 20 min. L-nitroarginine methyl ester (L-NAME, 40 mg/kg, i.p.) significantly inhibited post-exercise hypotension (25+/-11 and 5+/-3 mm Hg, respectively; P<0.05). In addition, the superoxide anion generation was decreased, while the plasma nitrite production and serine phosphorylation of endothelial nitric oxide synthase were significantly elevated in spontaneously hypertensive rats at 30 min after the termination of exercise. Taken together, these data demonstrate that the increased phosphorylation of endothelial nitric oxide synthase plays a crucial role in the reduction of arterial pressure following a single bout of dynamic exercise in spontaneously hypertensive rats.

Association of alpha1a-adrenergic receptor polymorphism and blood pressure phenotypes in the Brazilian population

BACKGROUND

The alpha1A-adrenergic receptor (alpha1A-AR) regulates the cardiac and peripheral vascular system through sympathetic activation. Due to its important role in the regulation of vascular tone and blood pressure, we aimed to investigate the association between the Arg347Cys polymorphism in the alpha1A-AR gene and blood pressure phenotypes, in a large sample of Brazilians from an urban population.

METHODS

A total of 1568 individuals were randomly selected from the general population of the Vitória City metropolitan area. Genetic analysis of the Arg347Cys polymorphism was conducted by polymerase chain reaction/restriction fragment length polymorphism. We have compared cardiovascular risk variables and genotypes using ANOVA, and Chi-square test for univariate comparisons and logistic regression for multivariate comparisons.

RESULTS

Association analysis indicated a significant difference between genotype groups with respect to diastolic blood pressure (p = 0.04), but not systolic blood pressure (p = 0.12). In addition, presence of the Cys/Cys genotype was marginally associated with hypertension in our population (p = 0.06). Significant interaction effects were observed between the studied genetic variant, age and physical activity. Presence of the Cys/Cys genotype was associated with hypertension only in individuals with regular physical activity (odds ratio = 1.86; p = 0.03) or younger than 45 years (odds ratio = 1.27; p = 0.04).

CONCLUSION

Physical activity and age may potentially play a role by disclosing the effects of the Cys allele on blood pressure. According to our data it is possible that the Arg347Cys polymorphism can be used as a biomarker to disease risk in a selected group of individuals.

Acute aerobic exercise reduces 24-h ambulatory blood pressure levels in long-term-treated hypertensive patients

BACKGROUND

Even with anti-hypertensive therapy, it is difficult to maintain optimal systemic blood pressure values in hypertensive patients. Exercise may reduce blood pressure in untreated hypertensive, but its effect when combined with long-term anti-hypertensive therapy remains unclear. Our purpose was to evaluate the acute effects of a single session of aerobic exercise on the blood pressure of long-term-treated hypertensive patients.

METHODS

Fifty treated hypertensive patients (18/32 male/female; 46.5+/-8.2 years; Body mass index: 27.8+/-4.7 kg/m(2)) were monitored for 24 h with respect to ambulatory (A) blood pressure after an aerobic exercise session (post-exercise) and a control period (control) in random order. Aerobic exercise consisted of 40 minutes on a cycle-ergometer, with the mean exercise intensity at 60% of the patient's reserve heart rate.

RESULTS

Post-exercise ambulatory blood pressure was reduced for 24 h systolic (126+/-8.6 vs. 123.1+/-8.7 mmHg, p=0.004) and diastolic blood pressure (81.9+/-8 vs. 79.8+/-8.5 mmHg, p=0.004), daytime diastolic blood pressure (85.5+/-8.5 vs. 83.9+/-8.8 mmHg, p=0.04), and nighttime S (116.8+/-9.9 vs. 112.5+/-9.2 mmHg, p<0.001) and diastolic blood pressure (73.5+/-8.8 vs. 70.1+/-8.4 mmHg, p<0.001). Post-exercise daytime systolic blood pressure also tended to be reduced (129.8+/-9.3 vs. 127.8+/-9.4 mmHg, p=0.06). These post-exercise decreases in ambulatory blood pressure increased the percentage of patients displaying normal 24h systolic blood pressure (58% vs. 76%, p=0.007), daytime systolic blood pressure (68% vs. 82%, p=0.02), and nighttime diastolic blood pressure (56% vs. 72%, p=0.02). Nighttime systolic blood pressure also tended to increase (58% vs. 80%, p=0.058).

CONCLUSION

A single bout of aerobic exercise reduced 24h ambulatory blood pressure levels in long-term-treated hypertensive patients and increased the percentage of patients reaching normal ambulatory blood pressure values. These effects suggest that aerobic exercise may have a potential role in blood pressure management of long-term-treated hypertensive.

Hypotensive effects of exercise performed around anaerobic threshold in type 2 diabetic patients

AIM

To verify the occurrence of post-exercise hypotension (PEH) in type 2 diabetics (DM(2)) and the effects of exercise intensity on post-exercise blood pressure (BP).

METHODS

Eleven men and women with DM(2) (58.5+/-10.2 years; 160+/-0.1cm; 80.6+/-13.5kg; 31.2+/-3.8kg/m(2), 19+/-3.2mLkgmin(-1) of VO(2max), 155.0+/-39.2mgdL(-1) of fasting blood glucose and 126+/-10/75+/-7mmHg of resting BP) performed an incremental test (IT) for cardiovascular evaluation and anaerobic threshold (AT) determination. Then, participants randomly underwent 2 exercise sessions (90% and 110% AT) and a control session (CON). In all sessions, BP was measured at resting, during 20min of exercise/control and at each 15min through 120min of post-exercise recovery (R15-R120).

RESULTS

The mean results of systolic BP (SBP)/diastolic BP (DBP) over the 120min of recovery were 125+/-16/76+/-7mmHg, 122+/-13/75+/-6mmHg and 129+/-16/78+/-7mmHg, respectively for 90%, 110% and CON. Significant reductions of SBP occurred after 90% (R15-R45) and 110% (R15-R90), while only after 110% there were reductions of DBP (R15, R45) and MAP (R15, R45, R75, R90, R105).

CONCLUSIONS

Both exercise intensities evoked reductions in SBP while DBP and MAP were reduced only after 110%. Despite the higher intensity exercise to be more effective in promoting BP reductions, we suggest caution while prescribing exercise for DM(2).

Post-resistance exercise hypotension in spontaneously hypertensive rats is mediated by nitric oxide

1. Postexercise hypotension (PEH) plays an important role in the non-pharmacological treatment of hypertension. It is characterized by a decrease in blood pressure (BP) after a single bout of exercise in relation to pre-exercise levels. 2. The present study investigated the effect of a single session of resistance exercise, as well as the effect of nitric oxide (NO) and the autonomic nervous system (ANS), in PEH in spontaneously hypertensive rats (SHR). 3. Catheters were inserted into the left carotid artery and left jugular vein of male SHR (n = 37) for the purpose of measuring BP or heart rate (HR) and drug or vehicle administration, respectively. Haemodynamic measurements were made before and after acute resistance exercise. The roles of NO and the ANS were investigated by using N(G)-nitro-L-arginine methyl ester (L-NAME; 15 mg/kg, i.v.) and hexamethonium (20 mg/kg, i.v.) after a session of acute resistance exercise. 4. Acute resistance exercise promoted a pronounced reduction in systolic and diastolic BP (-37 +/- 1 and -8 +/- 1 mmHg, respectively; P < 0.05), which was suppressed after treatment with L-NAME. The reduction in systolic BP caused by exercise (-37 +/- 1 mmHg) was not altered by the administration of hexamethonium (-38 +/- 2 mmHg; P > 0.05). After exercise, the decrease in diastolic BP was greater with hexamethonium (-26 +/- 1 mmHg; P < 0.05) compared with the decrease caused by exercise alone. 5. The results suggest that acute resistance exercise has an important hypotensive effect on SHR and that NO plays a crucial role in this response.

H2-receptor-mediated vasodilation contributes to postexercise hypotension

The early (∼30 min) postexercise hypotension response after a session of aerobic exercise is due in part to H1-receptor-mediated vasodilation. The purpose of this study was to determine the potential contribution of H2-receptor-mediated vasodilation to postexercise hypotension. We studied 10 healthy normotensive men and women (ages 23.7 ± 3.4 yr) before and through 90 min after a 60-min bout of cycling at 60% peak O2 uptake on randomized control and H2-receptor antagonist days (300 mg oral ranitidine). Arterial pressure (automated auscultation), cardiac output (acetylene washin) and femoral blood flow (Doppler ultrasound) were measured. Vascular conductance was calculated as flow/mean arterial pressure. Sixty minutes postexercise on the control day, femoral (Δ62.3 ± 15.6%, where Δ is change; P < 0.01) and systemic (Δ13.8 ± 5.3%; P = 0.01) vascular conductances were increased, whereas mean arterial pressure was reduced (Δ−6.7 ± 1.1 mmHg; P < 0.01). Conversely, 60 min postexercise with ranitidine, femoral (Δ9.4 ± 9.2%; P = 0.34) and systemic (Δ−2.8 ± 4.8%; P = 0.35) vascular conductances were not elevated and mean arterial pressure was not reduced (Δ−2.2 ± 1.3 mmHg; P = 0.12). Furthermore, postexercise femoral and systemic vascular conductances were lower ( P < 0.05) and mean arterial pressure was higher ( P = 0.01) on the ranitidine day compared with control. Ingestion of ranitidine markedly reduces vasodilation after exercise and blunts postexercise hypotension, suggesting H2-receptor-mediated vasodilation contributes to postexercise hypotension.

Is postexercise hypotension related to excess postexercise oxygen consumption through changes in leg blood flow?

After a single bout of aerobic exercise, oxygen consumption remains elevated above preexercise levels [excess postexercise oxygen consumption (EPOC)]. Similarly, skeletal muscle blood flow remains elevated for an extended period of time. This results in a postexercise hypotension. The purpose of this study was to explore the possibility of a causal link between EPOC, postexercise hypotension, and postexercise elevations in skeletal muscle blood flow by comparing the magnitude and duration of these postexercise phenomena. Sixteen healthy, normotensive, moderately active subjects (7 men and 9 woman, age 20–31 yr) were studied before and through 135 min after a 60-min bout of upright cycling at 60% of peak oxygen consumption. Resting and recovery V̇o2were measured with a custom-built dilution hood and mass spectrometer-based metabolic system. Mean arterial pressure was measured via an automated blood pressure cuff, and femoral blood flow was measured using ultrasound. During the first hour postexercise, V̇o2was increased by 11 ± 2%, leg blood flow was increased by 51 ± 18%, leg vascular conductance was increased by 56 ± 19%, and mean arterial pressure was decreased by 2.2 ± 1.0 mmHg (all P < 0.05 vs. preexercise). At the end of the protocol, V̇o2remained elevated by 4 ± 2% ( P < 0.05), whereas leg blood flow, leg vascular conductance, and mean arterial pressure returned to preexercise levels (all P > 0.7 vs. preexercise). Taken together, these data demonstrate that EPOC and the elevations in skeletal muscle blood flow underlying postexercise hypotension do not share a common time course. This suggests that there is no causal link between these two postexercise phenomena.

H1 receptor-mediated vasodilatation contributes to postexercise hypotension

In normally active individuals, postexercise hypotension after a single bout of aerobic exercise is due to an unexplained peripheral vasodilatation. Histamine has been shown to be released during exercise and could contribute to postexercise vasodilatation via H1 receptors in the peripheral vasculature. The purpose of this study was to determine the potential contribution of an H1 receptor-mediated vasodilatation to postexercise hypotension. We studied 14 healthy normotensive men and women (ages 21.9 +/- 2.1 years) before and through to 90 min after a 60 min bout of cycling at 60% on randomized control and H1 receptor antagonist days (540 mg oral fexofenadine hydrochloride; Allegra). Arterial blood pressure (automated auscultation) and femoral blood flow (Doppler ultrasound) were measured in the supine position. Femoral vascular conductance was calculated as flow/pressure. Fexofenadine had no effect on pre-exercise femoral vascular conductance or mean arterial pressure (P > 0.5). At 30 min postexercise on the control day, femoral vascular conductance was increased (Delta+33.7 +/- 7.8%; P < 0.05 versus pre-exercise) while mean arterial pressure was reduced (Delta-6.5 +/- 1.6 mmHg; P < 0.05 versus pre-exercise). In contrast, at 30 min postexercise on the fexofenadine day, femoral vascular conductance was not elevated (Delta+10.7 +/- 9.8%; P = 0.7 versus pre-exercise) and mean arterial pressure was not reduced (Delta-1.7 +/- 1.2 mmHg; P = 0.2 versus pre-exercise). Thus, ingestion of an H1 receptor antagonist markedly reduces vasodilatation after exercise and blunts postexercise hypotension. These data suggest H1 receptor-mediated vasodilatation contributes to postexercise hypotension.

Postexercise hypotension is not explained by a prostaglandin-dependent peripheral vasodilation

In normally active individuals, postexercise hypotension after a single bout of aerobic exercise occurs due to an unexplained peripheral vasodilation. Prostaglandin production has been suggested to contribute to the increases in blood flow during and after exercise; however, its potential contribution to postexercise hypotension has not been assessed. The purpose of this study was to determine the potential contribution of a prostaglandin-dependent vasodilation to changes in systemic vascular conductance underlying postexercise hypotension; this was done by inhibiting production of prostaglandins with the cyclooxygenase inhibitor ibuprofen. We studied 11 healthy normotensive men (aged 23.7 +/- 4.2 yr) before and during the 90 min after a 60-min bout of cycling at 60% peak O(2) uptake on a control and a cyclooxygenase inhibition day (randomized). Subjects received 10 mg/kg of oral ibuprofen on the cyclooxygenase inhibition day. On both study days, arterial blood pressure (automated auscultation) and cardiac output (acetylene uptake) were measured, and systemic vascular conductance was calculated. Inhibition of cyclooxygenase had no effect on baseline values of mean arterial pressure or systemic vascular conductance (P > 0.2). After exercise on both days, mean arterial pressure was reduced (-2.2 +/- 1.0 mmHg change with the control condition and -3.8 +/- 1.5 mmHg change with the ibuprofen condition, both P < 0.05 vs. preexercise) and systemic vascular conductance was increased (5.2 +/- 5.0% change with the control condition and 8.7 +/- 4.1% change with the ibuprofen condition, both P < 0.05 vs. preexercise). There were no differences between study days (P > 0.6). These data suggest that prostaglandin-dependent vasodilation does not contribute to the increased systemic vascular conductance underlying postexercise hypotension.

Exercise and endothelial function: role of endothelium-derived nitric oxide and oxidative stress in healthy subjects and hypertensive patients

Recent epidemiologic studies have shown that aerobic exercise, one of lifestyle modifications, reduces cardiovascular morbidity and mortality in the general population. However, the mechanisms underlying the anti-atherogenic and anti-hypertensive effects of exercise remain unclear. Hypertension is associated with alteration in endothelial function mediated through reduced nitric oxide (NO) bioavailability. Endothelial dysfunction is an early feature of atherosclerosis and vascular diseases in humans. Exercise training has been shown to improve endothelial function in animal models of hypertension and in patients with essential hypertension. These findings suggest that endothelial dysfunction in hypertension is reversible. Lifestyle modifications including exercise are expected to prevent cardiovascular complications through an augmentation of endothelial function in hypertensive patients. It is thought that exercise increases NO production and decreases NO inactivation, leading to an increase in NO bioavailability. In this review, we will focus on recent findings and on possible mechanisms underlying the beneficial effects of exercise on endothelial function in patients with hypertension.

American College of Sports Medicine position stand. Exercise and hypertension

Hypertension (HTN), one of the most common medical disorders, is associated with an increased incidence of all-cause and cardiovascular disease (CVD) mortality. Lifestyle modifications are advocated for the prevention, treatment, and control of HTN, with exercise being an integral component. Exercise programs that primarily involve endurance activities prevent the development of HTN and lower blood pressure (BP) in adults with normal BP and those with HTN. The BP lowering effects of exercise are most pronounced in people with HTN who engage in endurance exercise with BP decreasing approximately 5-7 mm HG after an isolated exercise session (acute) or following exercise training (chronic). Moreover, BP is reduced for up to 22 h after an endurance exercise bout (e.g.postexercise hypotension), with greatest decreases among those with highest baseline BP. The proposed mechanisms for the BP lowering effects of exercise include neurohumoral, vascular, and structural adaptations. Decreases in catecholamines and total peripheral resistance, improved insulin sensitivity, and alterations in vasodilators and vasoconstrictors are some of the postulated explanations for the antihypertensive effects of exercise. Emerging data suggest genetic links to the BP reductions associated with acute and chronic exercise. Nonetheless, definitive conclusions regarding the mechanisms for the BP reductions following endurance exercise cannot be made at this time. Individuals with controlled HTN and no CVD or renal complications may participated in an exercise program or competitive athletics, but should be evaluated, treated and monitored closely. Preliminary peak or symptom-limited exercise testing may be warranted, especially for men over 45 and women over 55 yr planning a vigorous exercise program (i.e. > or = 60% VO2R, oxygen uptake reserve). In the interim, while formal evaluation and management are taking place, it is reasonable for the majority of patients to begin moderate intensity exercise (40-<60% VO2R) such as walking. When pharmacological therapy is indicated in physically active people it should be, ideally: a) lower BP at rest and during exertion; b) decrease total peripheral resistance; and, c) not adversely affect exercise capacity. For these reasons, angiotensin converting enzyme (ACE) inhibitors (or angiotensin II receptor blockers in case of ACE inhibitor intolerance) and calcium channel blockers are currently the drugs of choice for recreational exercisers and athletes who have HTN. Exercise remains a cornerstone therapy for the primary prevention, treatment, and control of HTN. The optimal training frequency, intensity, time, and type (FITT) need to be better defined to optimize the BP lowering capacities of exercise, particularly in children, women, older adults, and certain ethnic groups. based upon the current evidence, the following exercise prescription is recommended for those with high BP: Frequency: on most, preferably all, days of the week. Intensity: moderate-intensity (40-<60% VO2R). Time: > or = 30 min of continuous or accumulated physical activity per day. Type: primarily endurance physical activity supplemented by resistance exercise.

Alpha-adrenergic vascular responsiveness during postexercise hypotension in humans

In sedentary individuals, postexercise hypotension following a single bout of aerobic exercise is due to an unexplained peripheral vasodilatation. We tested the hypothesis that alpha-adrenergic responsiveness in the forearm and leg vasculatures is blunted during postexercise hypotension. We studied 12 men and two women before and 30 min after a 60 min bout of cycling at 60 % VO2,peak. In the first five subjects, arterial pressure (brachial artery catheter) and forearm blood flow (plethysmography) were measured and vascular conductance was calculated during intraarterial infusions of the alpha1-agonist phenylephrine and the alpha2-agonist clonidine. Exercise reduced mean arterial pressure (89 +/- 2 vs. 95 +/- 2 mmHg, P < 0.05) and increased forearm vascular conductance 77 +/- 33 % (P < 0.05). Despite these changes in baseline vascular conductance, vasoconstrictor responses in the forearm to phenylephrine and clonidine were similar (or enhanced) postexercise vs. preexercise. In the remaining nine subjects, arterial pressure (femoral artery catheter) and leg blood flow (Doppler ultrasound of the femoral artery) were measured and vascular conductance was calculated during intraarterial infusions of phenylephrine and clonidine. Exercise reduced mean arterial pressure (80 +/- 2 vs. 89 +/- 2 mmHg, P < 0.05) and increased leg vascular conductance 94 +/- 16 % (P < 0.05). Despite these changes in baseline vascular conductance, vasoconstrictor responses in the leg to phenylephrine and clonidine were similar (or enhanced) postexercise vs. preexercise. These results suggest that vascular responsiveness to alpha-adrenergic agonists is maintained during postexercise hypotension in humans. Thus, while postexercise hypotension is associated with increased vascular conductance in the forearm and leg, it does not appear that blunting of alpha-adrenergic responsiveness is the cause.