Effects of sodium depletion on plasma renin activity and on the urinary excretion of cyclic AMP and aldosterone in hypoparathyroid patients.

The effect of sodium depletion on plasma renin activity (PRA), urinary cyclic AMP and urinary aldosterone excretion was studied in hypoparathyroid patients whose basal urinary cylic AMP excretion (urinary cAMP) was less than 50% of that observed in normal subjects. During 7 days of sodium depletion, PRA, urinary aldosterone and urinary cAMP each rose significantly. Administration of the beta-blocker propranolol, 160 mg/day, during 5 further days of sodium depletion produced a fall in PRA and urinary cAMP, but no change in urinary aldosterone excretion. The dissociation in these effects suggests that the increase in aldosterone secretion during sodium depletion may be mediated by pathways other than the renin-angiotensin and adenyl cyclase systems. There was a high degree of correlation between PRA and urinary cAMP (P less than 0.001) during the period of sodium depletion, but not significant relationship between these parameters was found during control and propranolol phases, or in control studies in normal subjects. These findings suggest that beta-adrenergic receptors have a role in mediating the effects of sodium depletion upon renin secretion and adenyl cyclase activity.

Beta-blockers and plasma renin activity in hypertension.

Long-term treatment with propranolol was shown to produce a sustained suppression of the renin-aldosterone system in hypertensive patients, despite concurrent diuretic treatment. However, the antihypertensive effect of this treatment correlated poorly with its effects on plasma renin activity and urinary aldosterone excretion. When prindolol, another beta-adrenergic blocking drug, was substituted for propranolol, blood pressure control was retained, but there was a prompt rise in plasma renin activity, which was not attributable to changes in electrolyte balance. These observations suggest that the antihypertensive action of propranolol and other beta-blockers does not result from their effects on plasma renin activity.

Alcohol consumption and blood pressure: survey of the relationship at a health-screening clinic.

We studied the association between stated alcohol consumption and blood pressure, making allowance for age, adiposity and smoking in 13535 men and 7385 women who were not receiving antihypertensive treatment. They represented a wide cross-section of the inner Sydney working population with 95% aged between 18 and 70. We found a high degree of linear correlation between stated alcohol consumption and blood pressure, diastolic and systolic. This relationship was independent of age, adiposity and smoking. For each 100 g/week increase in stated alcohol consumption, diastolic blood pressure increased by 0.12 kPa (0.92 mmHg) in men and by 0.20 kPa (1.5 mmHg) in women; no threshold for this effect was evident. A plateau appeared at about 500 g/week. Blood pressure increased significantly with age and adiposity (Quetelet's index). Smoking was associated with a lower diastolic blood pressure. The difference in mean diastolic blood pressure between smokers and non-smokers was 0.20 kPa (1.5 mmHg) for men and 0.27 kPa (2.1 mmHg) for women.

Combined use of prazosin and beta-blockers in hypertension.

Combined use of prazosin and beta-blockers in a hypertension clinic over a 3-year period was surveyed by means of a computerized record system. Of the 1,250 patients in the clinic, 171 (14%) had been treated with this combination for periods averaging 17 months. Prazosin was administered with a beta 1-selective beta-blocker in 94 cases and with a beta 1 + beta 2-blocker in 100 cases; 23 patients had received treatment with both combinations. Diuretics were given in 86% of cases and other antihypertensive drugs in 19%. The population treated had a high incidence of severe hypertension, with initial diastolic pressure greater than 120 mm Hg in 38% and between 100 and 120 mm Hg in 50%. The percentage of patients with diastolic pressure less than 100 mm Hg was 12% initially and 79% at the end of the treatment period. Side effects necessitated withdrawal of therapy in 35 cases. These were referable in 19 cases to prazosin and in 16 to beta-blockers. Prazosin was found to be more effective in lowering blood pressure in combination with beta 1-blockers than with beta 1 + beta 2-blockers, although there were fewer severe side effects with beta 1-blockers.