Acid- and cryoactivation of renin in human plasma.

Inactive renin in normal human plasma was activated in vitro either by cryoactivation (incubation at 0 degrees C/-5 degrees C up to 3 months) or acid-activation (dialysis to pH 3.0 for 48 h followed by diaylsis to pH 7.5). Plasma-renin-concentration was similar after either activation procedure (96 +/- 50 microU/ml vs 100 +/- 43 microU/ml). There was no further significant acid-activable renin after cryoactivation. These data suggest that conversion of inactive to active renin by optimized procedures is complete. The term "total renin" for activation results under these conditions seems to be valid.