Role of renal kallikrein in the regulation of blood pressure in the rat remnant kidney model of chronic renal failure.

We studied urinary excretion of active and inactive kallikrein every day for 3 weeks in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) subjected to 5/6 nephrectomy (5/6), 1/2-nephrectomy (1/2) or sham-operation (Sham). We determined urinary active and inactive kallikrein by measuring kallikrein activity using a kininogenase assay before and after treatment with trypsin (200 micrograms/ml). In the SHR group, blood pressure was significantly elevated in 5/6-animals as compared with 1/2 or sham, whereas in the WKY group blood pressure was not changed after either operation. Urinary active and total kallikrein excretion were decreased in 5/6-SHR to 34% and 59%, respectively, as compared with values of sham-SHR, and in 1/2-SHR to 70% and 70%, respectively. Similarly, they were also decreased in 5/6-WKY to 36% and 55%, respectively, as compared with values of sham-WKY. In 1/2-WKY urinary active kallikrein excretion was decreased to 88% as compared with the value of sham-WKY, but urinary total kallikrein excretion was not different from that of sham-WKY. Thus, the suppressed renal kallikrein activity due to reduced renal mass was not associated with any significant change in blood pressure in WKY, although it induced an elevation of blood pressure in SHR. These results indicate that the decreased production of renal active kallikrein may not play a significant role in the regulation of blood pressure in the rat remnant kidney model of chronic renal failure. In addition, it is suggested that the elevation of blood pressure in this model of SHR may be due to other factors than renal kallikrein.