1. Hepatic elimination of renin was measured in 10 well-compensated cardiac patients with normal liver function during a control period and during a period of reduced hepatic plasma flow, induced by physical exercise (seven patients) or intravenous infusion of lysine vasopressin (three patients).
2. Hepatic renin elimination rate (hepatic plasma flow × arterial-hepatic vein difference of plasma renin activity) was found to be linearly correlated with arterial plasma renin activity (r = 0.986, P < 0.001).
3. When hepatic plasma flow fell by 45% the hepatic extraction ratio of renin (arterial-hepatic vein plasma renin activity difference/arterial plasma renin activity) increased by 75%. Hepatic renin clearance (hepatic plasma flow × extraction ratio) remained constant.
4. The results indicate that changes in the hepatic elimination rate of renin do not contribute to changes in plasma renin activity during these events.