Effect Of Gap Junction On Endothelin And Phenylephrine-induced Vasoconstriction

BACKGROUND and OBJECTIVES Gap junctions are highly conductive channels that allow the direct transfer of intracellular messengers, ion and small molecules between interconnected cells. Gap junction channel is formed by head-to-head docking of two hemichannels (connexon), each composed of six connexin molecules,the basic component of gap junctions, hexagonally arranged around an aqueous pore. Fifteen members of rodent connexin family have been identified. It is found that connexins are expressed in most organs and tissues, except skeletal muscles and erythrocytes. At present, more interests are focused on nerve system and heart. The goal of this experiment is to detect the expression of connexins(Cx43 and Cx45) in rat mesenteric arteries and investigate the role of gap junctions(GJ) in the contraction induced by phenylephrine(PE) and endothelin(ET-1) in isolated rat mesenteric arteries. METHODS (1) The expression of Cx43 and Cx45 in rat mesenteric arteries was detected by immunohistochemistry. (2) Isolated rat mesenteric arterial rings experiment: ①The effect of pretreatment with 3.0×10-5,3.0×10-4 mol·L-1 Heptanol on 10nM ET-1-induced contraction in isolated rat mesenteric arterial rings (without and with endothelium) was investigated. ②The influence of Heptanol on 1.0×10-7 mol·L-1 PE-induced contraction in MARs(without and with endothelium) was researched. (3) Concentration-effect curves of PE in isolated rat mesenteric arterial rings pretreated by 3.0×10-5,1.0×10-4 ,3.0×10-4 mol·L-1 Heptanol were recorded as changes in isometric force. RESULTS (1) The immunohistochemical results indicated that two types of connexins (Cx43,45) were expressed in rat mesenteric arteries ,and the density of Cx 45 was much higher than that of Cx43. The Cx45 staining was mostly observed between vascular smooth muscle cells, and sparsely between endothelium cells or in adventitia. The Cx43 staining was mainly confined to endothelium cells and adventitia, expressed sparsely between vascular smooth muscle cells. (2) ①Statistical data showed there was no significant difference between the effects of pretreatment with Heptanol on 10n mol·L-1 ET-1-induced contraction in MARs without and with endothelium. However, there was significant difference between the effects of 3.0×10-5 mol·L-1 and 3.0×10-4 mol·L-1 Heptanol. ②There was no significant difference between the effects of pretreatment with Heptanol on PE-induced contraction in MARs without and with endothelium. however, there was significant difference between the effects of 3.0×10-5 mol·L-1 and 3.0×10-4 mol·L-1 Heptanol. (3) The pretreatment with 3.0×10-5,1.0×10-4,3.0×10-4 mol·L-1 Heptanol caused a right shift to the concentration-effect curves of PE, the maximal response of PE did not decrease, and the EC50 of PE was significantly increased. It suggested the effect of Heptanol was dependent of concentration.CONCLUSION (1)There are some differences between the expression of Cx45 and Cx43. (2) The gap junctions are involved in ET-1/PE induced contraction in MARs, and gap junction ,especially between SMCs, plays an important role in contraction. (3) The inhibitory effect of Heptanol is concentration-dependent.