Active and inactive kallikrein released by kidney slices from normotensive and hypertensive rats

The relative rates of release of active and inactive kallikrein were investigated in the rat kidney by studying in vitro kidney slices. The slices were kept in Warburg flasks in a Krebs-Ringer solution for 15 up to 60 minutes, and their kallikrein content and the kallikrein-like activity released by them were measured at different times. Renal kallikrein concentration from two-kidney, one clip hypertensive rats was less than in the sham-operated controls (p less than 0.01). Active kallikrein released into the bathing medium was 4.7 +/- 0.3 ng/mg/hr in normotensive rats (n = 10) and 3.3 +/- 0.3 in two-kidney hypertensive animals (n = 12); the difference between both groups was statistically significant (p less than 0.01). Inactive kallikrein is between 60% and 70% of the total kallikrein released by kidneys of normal and hypertensive rats. Thus, under the conditions of these experiments, the kidney slices were able to release a kallikrein-like enzyme in an active and an inactive form. The rate of active kallikrein released from slices of hypertensive animals was lower than in the normotensive controls.