[Studies on mode of cystine aminopeptidase production in the human placental chorionic villi and its effect on angiotensin II during pregnancy].

The production mechanism and physiological significance of cystine aminopeptidase in human placental chorionic villi were investigated with the following findings: The CAP activity of the lysosome fraction was the greatest (p less than 0.05) in each trimester. The CAP activity determined using Kato's method, which can separate lysosome better, was significantly (p less than 0.05) lower than in our lysosome fraction. CAP activity increased significantly after 30 min. (p less than 0.05) in a human chorionic villi culture continued to rise up to 60 min. (p less than 0.01) and then fell slightly. In the presence of angiotensin II, CAP activity increased rapidly for the first 30 min. and after 60 min. fell rapidly and continuously (p less than 0.01). With ADP and PGF2 alpha added it decreased insignificantly. With galactose and sialic acid, the increase was significant only at 30 min. after adding galactose. Thin layer chromatography of angiotensin II after incubation with partially purified CAP for 3 hr at 37 degrees C indicates that CAP splits angiotensin II. A chromatogram of the amino acid shows that 76n mol aspartic acid, 30n mol valine, 49n mol isoleucine, 22n mol tyrosine, 55n mol phenylalanine and 54n mol arginine separated from 1 mumol angiotensin II. These results suggest that CAP originates in other lysosomeseized granules and is an angiotensinase-like enzyme. Since it acts like angiotensinase, it is probably one of the factors maintaining the mother's blood pressure at normal levels during pregnancy.