A naturally occurring competitive inhibitor of pig kidney renin has been identified in human plasma. The inhibitor was shown to be α-1 anti-trypsin and the effect in vitro on the renin activity was examined. The slope in the Hill plot is compatible with the assumption of one-site competitive inhibition. Other proteinase inhibitors, such as α-2-macroglobulin and C1 inactivator, however, have no inhibitory effect on the renin-angiotensinogen reaction.
