Kinin stimulation of renin release in isolated rat glomeruli

Numerous studies have suggested that a functional relationship exists between the renal kallikrein-kinin and renin-angiotensin systems. We used an in vitro preparation of isolated glomeruli to study the effect of kinins on renin release. Glomeruli were harvested from the dissected cortices of rat kidneys by a passive sieving technique. They were then placed in chambers and superfused with aerated modified Krebs buffer, and the chamber effluent was collected during two sequential 10-min periods. Bradykinin at 10(-6) M increased renin release from 2.17 +/- 0.34 to 4.05 +/- 0.72 ng ANG I/min, and 10(-5) M bradykinin increased renin release from 3.51 +/- 0.64 to 8.94 +/- 1.27 ng ANG I/min. With albumin-modified buffer, 10(-5) M bradykinin stimulated renin release from 7.11 +/- 0.79 to 14.03 +/- 2.36 ng/min. Lys-bradykinin at 10(-5) M also increased renin release from 5.69 +/- 1.11 to 14.50 +/- 2.65 ng ANG I/min. However, neither of the inactive kinin analogues, [Tyr8]bradykinin or des-Arg9-bradykinin, had any effect on renin release. We found that isolated glomeruli were relatively free of kininase activity, in contrast to the high activity found in the kidney slice preparation or in rat plasma. These results suggest that biologically active kinins can stimulate renin release in an in vitro preparation that is free of degradative kininases and independent of hemodynamic and neural influences.