Aim To investigate the effects of iptakalim, a new structural potassium channel opener （KCO）, on intracellular calcium concentration ([Ca2+]i), protein kinase C （PKC）, and cAMP-dependent kinase （PKA） activities in rat tail artery smooth muscle cells （RTA-SMC）, and to analyze mechanisms involved in iptakalim reversing hypertensive vascular remodeling. Methods RTA-SMC was cultured and passages 3-4 were used for experiment. [Ca2+]i was measured by laser scanning confocal microscope after loaded with fluorescent indicator fluo-3-acetoxymethylester, and activities of PKA and PKC were detected by commercial assay kits （the nonradioactive PepTag system） following instructions. Results Compared with baseline, [Ca2+]i reduced significantly after iptakalim- or pinacidil-treatment at concentrations of 0.1, 1 and 10 (μmol·L-1), while diazoxide caused significant decrease at concentration of 1 and 10 (μmol·L-1). After preincubation with 1 (μmol·L-1) glibenclamide, [Ca2+]i was not significantly changed when iptakalim, pinacidil or diazoxide were added at concentration of 0.1 and 1 (μmol·L-1). Activities of PKA and PKC increased significantly by 1 μmol·L-1 iptakalim- or pinacidil-treatment, while 1 μmol·L-1 diazoxide induced significant change in activity of PKC but not in that of PKA. Conclusion The characteristics of iptakalim on [Ca2+]i, PKA and PKC are more or less similar to those of pinacidil. Iptakalim decreased [Ca2+]i while increased PKA and PKC activities of RTA-SMCs, which may contribute to its ability to reverse antihypertensive vascular remodeling.
