Ang-II-induced Ca influx is mediated by the 1/4/5 subgroup of the transient receptor potential proteins in cultured aortic smooth muscle cells from diabetic Goto-Kakizaki rats

Angiotensin-II (Ang-II) exerts many of its vascular effects, including the pathophysiological changes associated with type 2 diabetes, through changes in intracellular calcium concentration [Ca²⁺]_i. We sought to clarify the mechanism responsible for Ang-II-induced Ca²⁺ influx in cultured aortic VSMC using the Goto-Kakizaki (GK) rat model of type 2 diabetes. Ang-II-induced Ca²⁺ influx was blocked by neither VDCC nor c-src inhibition but was sensitive to inositol 1,4,5-trisphosphate receptor inhibition, lanthanide and the diacylglycerol analogue, oleoyl-2-acetyl-sn-glycerol. Since transient receptor potential canonical (TRPC)-3 gene expression was undetectable in both WKY and GK VSMCs and TRPC6 gene and protein expression were significantly down-regulated in GK, we believe the 1/4/5 subgroup of TRPC proteins plays a significant role. Furthermore, in GK VSMC the elevated calcium influx observed was not attributable to increased TRPC expression, but rather an alteration of TRPC activity.