Extrarenal prorenin in plasma requires an activator of renal origin

Plasma prorenin may be of renal or extrarenal origin, and its conversion to renin may be catalyzed by renal or extrarenal enzymes. We tested the effect of bilateral nephrectomy and sham bilateral nephrectomy on plasma renin and prorenin in dogs, using low (3 mg/ml) and high (5 mg/ml) concentrations of trypsin to activate the prorenin. In the nephrectomized dogs, active plasma renin quickly disappeared, whereas plasma prorenin (inactive renin) increased by up to 300% during the first 24 hours after surgery, suggesting that it was released rapidly from a major extrarenal source but not converted to renin in the absence of the kidneys. In the sham surgery (control) group, plasma renin activity increased by up to 400% in the first 24 hours but returned almost to baseline by 48 hours, whereas prorenin remained at the preoperative value or fell below it. The quantity of prorenin varied greatly between the groups according to the time after surgery and the different concentrations of trypsin used. In the nephrectomy group, low and high trypsin levels resulted in similar prorenin values during the first 3 hours, but later on, the high trypsin level resulted in about twice as much prorenin. In the control group, high trypsin levels generally produced lower prorenin values than did low trypsin levels. Since trypsin is believed to interact with endogenous convertase enzymes in converting prorenin, a high requirement for it after bilateral nephrectomy suggests that removal of the kidneys causes a deficiency of such convertases. Conversely, the low requirement for trypsin after the stress of sham surgery suggests enhanced plasma convertase activity in the presence of the kidneys.(ABSTRACT TRUNCATED AT 250 WORDS)