Response of serum total renin to ramipril and metoprolol in hypertensive patients

Abstract

Renin-angiotensin system has long been thought to be a classic endocrine negative feedback system in the pathophysiology of hypertension. Furthermore, angiotensin II formation was believed to be regulated by renin secreted from the kidneys. In contrast to these considerations is the identification of local angiotensin II production in other tissues than pulmonary vasculature. Prorenin, the molecular precursor of renin, has been assumed to be involved in local angiotensin II production because of its renin-like activity. Prorenin has also been found to be secreted from extrarenal sources, although a major part of it is derived from the kidneys. Increased concentration of total renin in serum has been proposed to be useful in identifying patients with active proliferative retinopathy in insulin-dependent diabetic patients. Renin-angiotensin system is strongly affected by angiotensin-converting enzyme (ACE) inhibitors and therefore the interfering effect of ACE inhibitor medication on total renin concentration should be known in order to interpret serum total renin concentrations. Nine hypertensive outpatients, all men, treated at the department of internal medicine in Turku University Central Hospital, received randomly 5 mg of ramipril or 95 mg of metoprolol once a day for 4 weeks. Ramipril significantly increased the mean value of total renin (191.9 ng/l vs 312.0 ng/l, p<0.01), but the metoprolol-induced increase in the concentration of serum total renin was insignificant. We conclude that the negative feedback mechanism in regulating renin and prorenin secretion was inhibited by ACE inhibitor ramipril but beta1-selective adrenoceptor antagonist metoprolol did not significantly change total renin concentration in serum.