Cardiovascular reactivity to isometric stress in patients with stable and borderline hypertension and in normotensive subjects. Effects of alpha sympatholytics and beta blocking agents

Aim of the study was to evaluate blood pressure (BP) and heart rate (HR) variability during isometric handgrip test (IHT) in 20 ambulant non-obese male adults affected by sustained hypertension (SH) WHO I and II, 20 borderline hypertensive (BH) and 20 normotensives (C) of comparable sex, age and BMI. SBP and DBP were assessed by "Random Zero" sphygmomanometer, HR by ECG registration. IHT was performed at 30% of maximal effort for 3 min. IHT was carried out: 1) after 7 days placebo, 2) after 7 days propranolol treatment (80 mg/day) and, following 10 days wash-out, 3) after 7 days prazosin treatment (0.5 mg/day). After placebo IHT caused increases of SBP, DBP and HR values insignificantly different in the 3 groups. After propranolol IHT induced significantly more elevated SBP and DBP increases in SH than in BH or in C. These increases were significantly more elevated in comparison with those observed, in advance, in the same group of SH subjects after placebo. After prazosin treatment SBP increase induced by IHT was, on the contrary, significantly more elevated in BH than in SH or in C. This increase is more significant in comparison with that observed in the same BH group after placebo treatment. As for DBP variations induced by IHT after alpha sympatholytic therapy we have observed that SH subjects show significantly lesser diastolic variations as compared with those obtained in BH or in C groups after this treatment. In conclusion, enhanced IHT induced SBP elevation after propranolol and dampened DBP reactivity after prazosin suggest an overriding alpha stimulation in SH subjects. SBP hyperreactivity induced by IHT after alpha sympatholytic treatment and DBP hyporeactivity after betablockers emphasize the role of beta stimulation in BH individuals. Inhibition of BP reactivity to IHT in C after prazosin suggest that this one is mediated by alpha adrenergic receptors.