ATP-SENSITIVE POTASSIUM CHANNELS MEDIATE VASODILATATION PRODUCED BY CALCITONIN-GENE-RELATED PEPTIDE IN HUMAN INTERNAL MAMMARY BUT NOT GASTROEPIPLOIC ARTERIES

The purpose of this study was to elucidate the mechanism of action of calcitonin gene-related peptide-induced vasodilatation of human gastro epiploic and internal mammary arteries. Calcitonin gene-related peptid e (0.1-100 nmolL(-1)) elicited relaxations of pre constricted vessels, with a significantly greater effect in the gastroepiploic artery (P < 0.05). This effect was independent of endothelium-derived vasodilatin g substances. The response of the internal mammary artery but not the gastroepiploic artery to calcitonin gene-related peptide was attenuate d by glybenclamide (1.0 mu molL(-1)) (P < 0.05). In vitro autoradiogra phy indicated that [I-125]-calcitonin gene-related peptide bound to th e tunica media but not the endothelial cells in both types of artery, with a significantly higher degree of binding in the gastroepiploic ar tery. It is concluded that calcitonin gene-related peptide acts direct ly on vascular smooth muscle via specific binding sites to induce vaso dilatation. In addition, K-ATP channels are involved in the action of calcitonin gene-related peptide in the internal mammary artery but not in the gastroepiploic artery.