Solution of methodological problems in measurement of inactive renin in rat plasma using trypsin activation, and the effect of nephrectomy and sialo-adenectomy on inactive plasma renin.

Abstract

Trypsin activation of rat plasma destroys angiotensinogen and generates a tetradecapeptide-like material, verified by high performance liquid chromatography, which interferes with the measurement of inactive renin. Using an assay based on removal of the material by a cation-exchange resin and the addition of exogenous angiotensinogen, the plasma concentration of inactive renin in intact conscious male rat was 0.48 GU/l (range 0.28-0.67 GU/l, n = 20). Inactive renin comprised about 70% of the total plasma renin. The level of inactive renin was unchanged 24 h after bilateral nephrectomy and 7 days after submandibular sialo-adenectomy. Bilateral nephrectomy of previously sialo-adenectomized rats decreased the level of inactive renin significantly. Our findings are in contrast to the marked increase, reported by several other investigators, in inactive plasma renin in rats following bilateral nephrectomy, and do not support the previously suggested, mainly extrarenal, origin of inactive plasma renin.