Regulation of inactive renin secretion: studies with aprotinin

The kidney and plasma of many species contain both an active form of renin and an inactive, but activatable, form. The kallikrein inhibitor aprotinin suppressed acid-activation of rabbit plasma inactive renin but not activation of the form of inactive renin released by rabbit kidney cortex slices incubated in vitro. This suggests that inactive renin is structurally modified after secretion. An aprotinin-sensitive step appears to regulate inactive renin secretion. Aprotinin inhibited inactive, but not active, renin secretion by rabbit kidney cortex slices and selectively suppressed the elevated release of inactive renin produced in sheep by the converting enzyme inhibitor enalapril. In anaesthetised rats, aprotinin potentiated the increase in plasma renin produced by captopril.