Spontaneous inhibition or inactivation of renin in rat plasma

Renin appears to be rapidly inactivated in vitro. The present study was undertaken to clarify this observation and to establish the existence of substances involved in renin inactivation. The disappearance rate of renin (including pure renin) was measured in plasma incubated at 37 degrees C and in circulating blood. Pure renin added to plasmas disappears in vitro at the same rate (t(1/2) congruent to 40 min) that renin in plasma from normal rats and from rats submitted to a hemorrhage. This process appears not to be mediated by proteases. The disappearance rate of endogenous renin in the normal group (n = 18) was 39.7 min with a rapid phase (R) of t(1/2) = 14.2 min and a slow phase (S) of t(1/2) = 94.3 min), whereas it was 32.1 min (t(1/2) R = 13.1 min and t(1/2) S = 69.1 min) in rats submitted to an hemorrhage (n = 6). The t(1/2) of pure renin was 31.4 min (t(1/2) R = 13.3 min and t(1/2) S = 69.2 min). incubation of plasma reveals that renin is inactivated or inhibited in vitro at a similar rate than in circulating plasma. These results suggest that inactivation and sequestration of renin could be two independent mechanisms in the maintenance of plasma renin activity. Copyright (C) 1997 Elsevier Science Inc.