Differential secretion and removal of multiple renin forms.

Hepatic clearance of renin in anesthetized dogs was measured during aortic constriction and after nephrectomy. Aortic constriction caused a transient increase in the hepatic extraction ratio for renin (ER) from 0.34 +/- 0.05 to 0.52 +/- 0.05, whereas nephrectomy caused the ER to decrease with time. Isoelectric focusing of plasma samples over an average pH gradient of 4.0-6.2 yielded several peaks of renin activity. Peaks focusing above pH 5.0 were combined and arbitrarily classified as basic renin, whereas peaks below pH 5.0 were classified as acidic renin. In each period the ER for basic renin was significantly greater than that for acidic renin. The proportion of basic renin was transiently increased at 10 min (59 +/- 4%) compared with control (41 +/- 4%). This contributed to the increased ER after constriction. The decreased ER after nephrectomy, however, was not solely due to differential removal of these forms. We conclude that hepatic clearance of renin is partly a function of the type of renin secreted by the kidney, which in turn may change with the duration of the secretory stimulus.