The effect of proteolytic activity on plasma renin activity assay

Carrier proteins are used in the radioimmunoassay of angiotensin I. It has been shown that the proteolytic activity found in commercial lysozyme will falsely elevate the observed plasma renin activity. This effect is probably due to the fact that human plasma contains proteinase inhibitors which inhibit this activity during radioimmunoassay of angiotensin I. This proteolytic activity can be inhibited by diisopropyl fluorophosphate or by heating lysozyme.