Functional up-regulation of KCNA gene family expression in murine mesenteric resistance artery smooth muscle

This study focused on the hypothesis that KCNA genes (which encode K_vα1 voltage-gated K⁺ channels) have enhanced functional expression in smooth muscle cells of a primary determinant of peripheral resistance-the small mesenteric artery. Real-time PCR methodology was developed to measure cell type-specific in situ gene expression. Profiles were determined for arterial myocyte expression of RNA species encoding K_vα1 subunits as well as K_vβ1, K_vα2.1, K_vγ9.3, BK_Caα1 and BK_Caβ1. The seven major KCNA genes were expressed and more readily detected in endothelium-denuded mesenteric resistance artery compared with thoracic aorta; quantification revealed dramatic differential expression of one to two orders of magnitude. There was also four times more RNA encoding K_vα2.1 but less or similar amounts encoding K_vβ1, K_vγ9.3, BK_Caα1 and BK_Caβ1. Patch-clamp recordings from freshly isolated smooth muscle cells revealed dominant K_vα1 K⁺ current and current density twice as large in mesenteric cells. Therefore, we suggest the increased RNA production of the resistance artery impacts on physiological function, although there is quantitatively less K⁺ current than might be expected. The mechanism conferring up-regulated expression of KCNA genes maybe common to all the gene family and play a functional role in the physiological control of blood pressure.