Kallikreinlike activity in perfusates and urine of isolated rat kidneys

In the perfusate and the urine produced during perfusion of isolated rat kidneys a kallikreinlike enzyme similar to that found in the kidney was detectable by bioassay 15-25 min after the beginning of the perfusion. The source of the kallikrein activity was the kidney itself, since before the perfusion was started the blood remaining in the kidneys was washed out and the perfusion medium was free of kallikrein and its precursors and substrates. The kallikreinlike activity of the perfusate was characterized by a) an oxytocic effect on isolated rat uterus, b) a kininogenase activity on kininogen II, c) an esterase activity on N-benozyl-L-arginine ethyl ester, and d) a hypotensive effect on anethetized rats. These properties were inhibited by diisopropyl activity in the perfused kidney was lower than that in the nonperfused organ, but the total amount of kallikrein activity released to the excreted urine and the perfusate was significantly greater than the corresponding activity that disappeared in the kidney. This result is in keeping with the concept that the renal tissue is able to synthesize kallikrein.