Correlation of plasma angiotensin II concentration and plasma renin activity during acute hypoxia in dogs

The effects of isocapnic hypoxia on plasma renin activity (PRA) and angiotensin II (AII) concentration were studied in anaesthetized, artificially ventilated dogs. Regression analysis of plasma AII concentration vs PRA, both measured by radioimmunoassay (RIA), was used as an index of converting enzyme activity in vivo. PaO2 decreased from 82 to 30 mmHg but regression analysis did not reveal any inhibition of AII production within the limits of detection of this method (less than 20% inhibition). We conclude that systemic converting enzyme activity, assessed by in vivo measurement and correlation of PRA and AII, is not inhibited by severe hypoxia.