Expression of Ca-activated K Channels and Their Role in Proliferation of Rat Cardiac Fibroblasts.

Cardiac fibroblasts constitute one of the largest cell populations in the heart, and contribute to structural, biochemical, mechanical and electrical properties of the myocardium. Nonetheless, their cardiac functions, especially electrophysiological properties, have often been disregarded in studies. Ca(2+)-activated K(+) (K(Ca)) channels can control Ca(2+) influx as well as a number of Ca(2+)-dependent physiological processes. We, therefore, attempted to identify and characterize K(Ca) channels in rat Cardiac fibroblasts. First, we showed that the cells cultured from the rat ventricle were cardiac fibroblasts by immunostaining for discoidin domain receptor 2 (DDR-2), a specific fibroblast marker. Secondly, we detected the expression of various K(Ca) channels by reverse transcription polymerase chain reaction (RT-PCR), and found all three family members of K(Ca) channels, including large conductance K(Ca) (BK-alpha1- and -beta1~4 subunits), intermediate conductance K(Ca) (IK), and small conductance K(Ca) (SK1~4 subunits) channels. Thirdly, we recorded BK, IK, and SK channels by whole cell mode patch clamp technique using their specific blockers. Finally, we performed cell proliferation assay to evaluate the effects of the channels on cell proliferation, and found that the inhibition of IK channel increased the cell proliferation. These results showed the existence of BK, IK, and SK channels in rat ventricular fibroblasts and involvement of IK channel in cell proliferation.