Clarification of molecular mechanisms of endothelium-derived hyperpolarizing factor

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The purpose of this study was to clarify the molecular mechanisms of endothelium-derived hyperpolarizing factor (EDHF)-mediated arterial relaxation and membrane hyperpolarization in the rat mesenteric arteries. We tried to identify the ion channels, gap junctional channels and trp channels involved in the EDHF action. RT-PCR experiment showed that mRNA of small-conductance Ca^<2+>-activated K^+ (SK)3, intermediate-conductance Ca^<2+>-activated K^+(IK), large-conductance Ca^<2+>-activated K^+ (BK) channels and connexin-37, -40, -43, -45 but not SK1 and SK2 were exist in the rat mesenteric artery. cDNA of these ion channels and connexins were cloned by RT-PCR and cDNA library screening. New gene (SK3-b) similar to SK3 channel was cloned. The poly glutamine position of SK3 was substituted to poly serine in SK3-b. Functional analysis using patch clamp techniques showed that the SK3-b channel has almost the same ion channel functions such as voltage dependency and toxin sensitivity. However the Ca^<2+> sensitivity of the channel was less sensitive compared with that of the SK3. Immunohistochemical analysis showed that the SK3 channel was expressed in the endothelium. The CX37 and 43 were expressed in both the endothelial and smooth muscle cells, however CX40 was expressed in only the endothelial cells. To clarify the functional role of these genes in the native artery, adenoviruses expressing these genes were constructed. Adenovirus-mediated expression of SK3 or CX43 to the cultured rat mesenteric artery enhanced EDHF action slightly. Ovariectomy reduced the EDHF action in accordance with the reduced expression of CX40 and CX43