Influence of Sex on Gap Junctional Distribution and Vascular Dilatation in the Rat Mesenteric Arteries

Abstract

Background: Besides prostacyclin and nitric oxide, the endothelium-derived hyperpolarizing factor (EDHF), which is another distinct endothelium-dependent vasodilator, is involved in relaxing the vascular smooth muscle cells. The myoendothelial gap junction (MEGJ) and female sex hormone play important roles in the EDHF-mediated responses. Therefore, this study was designed to determine the influence of gender on the gap junctional distribution and endothelium-dependent vasodilation in the rat mesenteric arteries. Methods: Male and female Sprague-Dawley rat were euthanized and the tertiary branch of the mesenteric artery was harvested. Immunohistochemistry and confocal microscopic examination of the arterial wall were performed after treating them with specific antibodies to delineate the distribution of connexin 43, a gap junctional protein. Segments of the mesenteric artery, 5 mm in length, were connected to two tungsten wires under isometric tension. The arterial segments were suspended in a modified Krebs solution () aerated with 95% and 5% in a vertical water-jacketed temperature-controlled tissue bath. The standard dose-response curve for acetylcholine (- M) was drawn in the presence of the NO synthase inhibitor, -nitro-L-arginine methyl ester (L-NAME; M) plus indomethacin ( M) and/or gap junctional inhibitor, carbenoxolone ( M). Results: In the female rat mesenteric artery, the gap junctional plagues were more prevalent particularly along the endothelial layer. The inhibition of the relaxation response to acetylcholine was depressed in the presence of L-NAME plus indomethacin and augmented in the presence of carbenoxolone when compared with the male rat mesenteric arteries (P ＜ 0.05). Conclusions: Gender differences in the rat mensenteric arteries have an effect on the expression of connexin 43 and the release of EDHF through MEGJ may play a key role in controlling the female arterial tone.