Function of the autonomic nervous system in young, untreated hypertensive patients

Differential effects of eplerenone versus amlodipine on muscle metaboreflex function in hypertensive humans

Numerous studies have demonstrated that sympathetic nervous system overactivation during exercise in hypertensive rodents and humans is due, in part, to an exaggerated reflex response known as the exercise pressor reflex. Our prior studies have implicated a key role of mineralocorticoid receptor activation in mediating an augmented exercise pressor reflex in spontaneously hypertensive rats, which is mitigated by blockade with eplerenone. However, the effect of eplerenone on exercise pressor reflex has not been assessed in human hypertension. Accordingly, the authors performed a randomized crossover study to compare the effects of eplerenone to another antihypertensive drug from a different class amlodipine on sympathetic nerve activity (SNA) in 14 patients with uncomplicated hypertension. The authors found that amlodipine unexpectedly augmented the increase in SNA during the second minute of isometric handgrip, which persisted into the post‐exercise circulatory arrest period (∆ SNA, from rest of 15 ± 2 vs. 9 ± 2 vs. 10 ± 2 bursts/min, amlodipine vs. baseline vs. eplerenone, respectively, p < .01), suggesting an exaggerated muscle metaboreflex function. Eplerenone did not alter sympathetic responses to exercise or post‐exercise circulatory arrest in the same hypertensive individuals. In conclusions, our studies provide the first direct evidence for a potentially unfavorable potentiation of muscle metaboreflex by amlodipine during isometric handgrip exercise in hypertensive patients whereas eplerenone has no significant effect. Our study may have clinical implications in terms of selection of antihypertensive agents that have the least detrimental effects on sympathetic neural responses to isometric exercise.

Blood pressure and heart rate dynamics during and after exercise in an unselected population

It has been suggested that the systolic blood pressure (SBP) response to exercise may be useful in predicting future hypertension. However, controversy exists as to whether the SBP response to exercise in borderline hypertensives is actually greater than normotensives or merely increases equally but from a higher resting value. Our aim was to determine the influence of resting SBP, age and sex on changes of SSP during exercise for both healthy subjects and untreated mild hypertensives. Three hundred and eighteen (230 males) underwent a self limited exercise protocol. SBP was measured at baseline and between the 2nd and 3rd minutes of each exercise stage. Age was positively related to SBP at rest and during exercise. The magnitude of SBP change induced by exercise was similar irrespective of the level of resting SBP. The relationship between resting SBP and the absolute SBP change which occurred during exercise was independent of sex. Our findings indicate that (i) age is positively related to SBP at rest and during exercise, (ii) SBP rises equally during exercise irrespective of its resting level and (iii) males and females have a similar pattern of BP response to exercise.

Furosemide dynamics in conscious rabbits: modulation by angiotensin II

The aim of this study was to investigate the effects of an infusion of angiotensin II (50 ng/kg/min) on furosemide pharmacodynamics and kinetics in the conscious rabbit. The protocol included a 90-minute phase to estimate the glomerular filtration rate and the renal plasma flow, followed by a 60-minute phase where 5 mg/kg (n = 12) or 10 mg/kg (n = 9) of furosemide were administered. During the pre-furosemide phase, compared to control rabbits, angiotensin II increased natriuresis and diuresis. In the presence of angiotensin II, the furosemide-induced natriuresis decreased, that is, it was 174 +/- 14 versus 95 +/- 25 mumol/min (p < 0.05) and 187 +/- 17 versus 89 +/- 21 mumol/min (p < 0.05) for the 5 and the 10 mg/kg doses, respectively. The infusion of angiotensin II decreased renal plasma flow without modifying the glomerular filtration rate, thus the filtration fraction was increased. Angiotensin II increased the area under the furosemide plasma concentrations as a function of time since it decreased its systemic clearance. However, furosemide urinary excretion rate was not altered and its renal clearance decreased slightly without reaching statistical significance. It is concluded that angiotensin II decreases the response to furosemide and the mechanism underlying this effect is related to the pharmacodynamics rather than the kinetics of the diuretic.