Voltage-gated calcium channels (Cav) play an essential role in regulation of renal blood flow and GFR. Because T-type Cavs are differentially expressed in pre- and postglomerular vessels it was hypothesized that they impact renal blood flow and GFR differentially. The question was addressed by use of two T-type Cav knock-out mice strains. Continuous recordings of blood pressure and heart rate, and para-aminohippurate clearance (renal plasma flow) and inulin clearance (GFR) were performed in conscious, chronically catheterized, wild type and Cav 3.1-/- and Cav 3.2-/- mice. Contractility of afferent and efferent arterioles was determined in isolated perfused blood vessels. Efferent arterioles from Cav 3.2-/- mice constricted significantly more in response to a depolarization compared to Wt mice. GFR was increased in Cav 3.2-/- mice with no significant changes in renal plasma flow, heart rate and blood pressure. Cav 3.1-/- mice had a higher renal plasma flow compared to Wt, whereas GFR was indistinguishable from Wt. No difference in concentration-response to K+ was observed in isolated afferent and efferent arterioles from Cav 3.1-/- compared to Wt. The heart rate was significantly lower in Cav 3.1 KO compared to Wt with no difference in blood pressure. T-type antagonists significantly inhibited the constriction of human intra-renal arteries in response to a small depolarization. In conclusion, Cav 3.2 channels support dilatation of efferent arterioles and affect GFR while Cav 3.1 channels in vivo contribute to renal vascular resistance. It is suggested that endothelial and nerve localization of Cav 3.2 and Cav 3.1, respectively, may account for the observed effects.
American Journal of Physiology: Renal Physiology, 2014, Vol 307, Issue 4