Effect of dietary protein on glomerular renin secretion

Previous studies from our and other laboratories demonstrated that dietary protein restriction lowers plasma renin activity by impairing renin release. The effect of protein intake on glomerular renin secretion has not been investigated. Accordingly, we studied male Sprague-Dawley rats weighing 180 to 200 g for 3 weeks that were receiving isocaloric diets that provided either standard 20% protein (SP) or low 6% protein (LP). Renin secretion was measured in the glomeruli isolated from these rats, at baseline and following stimulation with arachidonic acid and isoproterenol. The activity of plasma renin (3.0 +/- 0.5 ng/mL/min on SP v 1.1 +/- 0.1 ng/mL/min on LP) was significantly (P < 0.02) lower on LP intake. In contrast, glomerular renin content (22.9 +/- 0.7 ng/micrograms protein on SP v 32.3 +/- 1.4 ng/micrograms protein on LP) was significantly (P < 0.01) higher on the LP diet. Furthermore, renin secretion (ng/mL/h) from the isolated glomeruli at baseline (3.9 +/- 1.0 on SP v 12.5 +/- 3.0 on LP, P < 0.02), and following incubation with arachidonic acid 10(-5) mol/L (5.9 +/- 1.7 on SP v 19.6 +/- 3.1 on LP, P < 0.005), and isoproterenol 10(-3) mol/L (6.0 +/- 0.5 on SP v 17.3 +/- 3.3 on LP, P < 0.01) was significantly higher on the LP diet. These studies suggest that dietary protein restriction impairs in vivo renin release. In contrast, in vitro glomerular renin release is augmented by protein restriction. The factors modulating in vivo renin release require further characterization.