THE EFFECT OF ISOPRENALINE ON PLASMA RENIN ACTIVITY IN MAN: A DOSE‐RESPONSE CURVE

SUMMARY Four normal subjects on a free sodium intake received intravenous isoprenaline in doses of 2, 4, 8 and 16 μg over 2 min. Three of the subjects received a second infusion of 8 μg. The rate of renin release indexed by changes in plasma renin activity increased in all subjects at each dose level. The mean peak leveles of plasma renin were 9%, 29% and 77% above the mean control levels at doses of 2, 4 and 8 μMg respectively. The response of 16 μg was no different from that seen with 8 μg. The renin response obtained at 8 μg was highly reproducible such that the coefficient of variation for duplicate estimations of plasma renin (twelve duplicates) ranged from 1.7 to 4%. The rate of renin release from the kidney is known to be under adrenergic control (Vander, 1965; Wathen et al., 1965; Allison et al., 1970; Ueda et al., 1973) and recent studies in animals and man have indicated that an intrarenal beta-adrenoreceptor mediates this release (Tobert et al., 1973; Inoue, 1973; Vandongen et al., 1973; Sabto et al., 1975). Isoprenaline is the archetypal beta-adrenergic agonist with equal effects upon both beta1 and beta2 receptors (Lands et al., 1967). We have previously shown that minute bolus injections of this agent provokes renin release in normal people (Davies et al., 1975). However, there appears to have been no systematic investigation of a dose-response relationship for the release of renin provoked by isoprenaline in man. The aim of this study was to attempt to define such a relationship and, mindful of the possible application of this technique to studies of the adrenergic control of renin release in patients, we have documented the reproducibility of this response.