Contribution of calmodulin and protein kinase C to renin release in spontaneously hypertensive rats. This study was designed to evaluate the contribution of calmodulin and protein kinase C to renin release from isolated glomeruli of spontaneously hypertensive rats (SHR, Okamoto and Aoki). Male 7-week-old SHR and age-matched control Wistar-Kyoto rats (WKY) were used in this study. Isolated glomeruli were sealed in the superfusion chamber and perfused with Krebs-Ringer solution at a constant flow of 0.3 mL/min. Renin release was increased by calmodulin inhibitor, W-7, and protein kinase C inhibitor, H-7, in both SHR and WKY. SHR showed higher maximal levels of renin release by W-7 and lower maximal levels by H-7 compared to WKY. These results indicate that calmodulin and protein kinase C play inhibitory roles in renin release from juxtaglomerular cells. The calmodulin-mediated suppression mechanism in renin release appears to be augmented in the SHR, whereas the protein kinase C-mediated system is attenuated. 