HALF-LIFE, HEMODYNAMIC, RENAL, AND HORMONAL EFFECTS OF PRORENIN IN CYNOMOLGUS MONKEYS

Prorenin is found in human plasma, kidneys, and reproductive organs. We investigated the physiological and pharmacokinetic properties of plasma prorenin, and its plasma conversion to active renin, by bolus infusions of human recombinant prorenin (0.5, 2, 20-mu-g; n = 4/dose) into anesthetized male cynomolgus monkeys. The infused prorenin had 3% intrinsic renin activity. Plasma prorenin rose from 61 +/- 6 to 101 +/- 11, 570 +/- 46, and 7,700 +/- 390 ng.ml-1.h-1, respectively, after 5 min. Plasma renin increased to 3% of total renin, angiotensin II increased less than twofold, and aldosterone did not change. Plasma testosterone fell slightly (P < 0.01). Mean arterial pressure (MAP) fell slowly from 104 +/- 3 to 93 +/- 3 mmHg at 60 min (P < 0.001). Heart rate, glomerular filtration rae, renal plasma flow, and urinary sodium and potassium excretion were unchanged. For the 2- and 20-mu-g doses, respectively, effective half-life of plasma decay was 47 +/- 4.9 and 109 +/- 21 min (P < 0.05), apparent volume of distribution was 145 +/- 11 and 166 +/- 35 ml/kg, and metabolic clearance rate was 2.30 +/- 0.44 and 1.08 +/- 0.14 ml.min-1.kg-1 (P < 0.01). In conclusion, neither the hormonal nor the physiological response to infusion of pharmacologic levels of recombinant human prorenin into monkeys provide evidence for conversion of circulating prorenin to renin. MAP did not increase and actually fell without commensurate effects on renal function. The half-life of recombinant prorenin was similar to that of renin.