A TRPC-like non-selective cation current activated by α1-adrenoceptors in rat mesenteric artery smooth muscle cells

The TRPC family of non-selective cation channels has been suggested to play a key role in the responses to alpha(1)-adrenoceptor stimulation of vascular smooth muscle. However, there are still very few reports of non-selective cation currents activated by alpha(1)-AR in resistance arteries. Here, we examine the expression of TRPC channels and the currents activated by alpha(1)-adrenoceptors in rat mesenteric resistance artery smooth muscle. Messenger RNA and protein for TRPC 1, TRPC3 and TRPC6 were detected within the arteries by RT-PCR and immunoblotting. Endothelial and adventitial layers were found to express the TRPC 1, TRPC3 and TRPC6 proteins whereas only TRPC1 and TRPC6 were detected in the arterial smooth muscle by confocal immunofluorescence microscopy. In whole-cell patch-clamp recordings from isolated mesenteric arterial myocytes, an outwardly rectifying non-selective cation current was activated by both the alpha(1)-adrenoceptor agonist, phenylephrine (10 mu M), and the diacylglycerol analogue, 1-oleoyl-2-acetyl-sn-glycerol (100 mu M). Responses to 1-oleoyl-2-acetyl-sn-glycerol were not blocked, but increased, following inhibition of protein-kinase-C with either bisindolylmaleimide-l (1 mu M) or chelerythrine (1 mu M). The currents activated by both phenylephrine and 1-oleoyl-2-acetyl-sn-glycerol were inhibited by Gd3+ (100 mu M) but potentiated by flufenamic acid (100 mu M). Collectively, these findings demonstrate for the first time the expression of TRPC1 and TRPC6 in rat mesenteric artery smooth muscle and the existence in rat isolated mesenteric arterial myocytes of a TRPC-like non-selective cation current activated by alpha(1)-adrenoceptor stimulation and 1-oleoyl-2-acetyl-sn-glycerol. (c) 2006 Elsevier Ltd. All rights reserved.