K-ATP channels regulate mitogenically induced proliferation in primary rathepatocytes and human liver cell lines - Implications for liver growth control and potential therapeutic targeting

To determine whether K-ATP channels control liver growth, we used primary r at hepatocytes and several human cancer cell lines for assays. K-ATP channe l openers (minoxidil, cromakalim, and pinacidil) increased cellular DNA syn thesis, whereas K-ATP channel blockers (quinidine and glibenclamide) attenu ated DNA synthesis. The channel inhibitor glibenclamide decreased the clono genicity of HepG2 cells without inducing cytotoxicity or apoptosis. To demo nstrate the specificity of drugs for K+ channels, whole-cell patch-clamp re cordings were made. Hepatocytes revealed K+ currents with K-ATP channel pro perties. These K+ currents were augmented by minoxidil and pinacidil and at tenuated by glibenclamide as well as tetraethylammonium, in agreement with established responses of K+, channels. Reverse transcription of total cellu lar RNA followed by polymerase chain reaction showed expression of K-ATP ch annel-specific subunits in rat hepatocytes and human liver cell lines. Calc ium fluxes were unperturbed in glibenclamide-treated HepG(2) cells and prim ary rat hepatocytes following induction with ATP and hepatocyte growth fact or, respectively, suggesting that the effect of K-ATP channel activity upon hepatocyte proliferation was not simply due to indirect modulation of intr acellular calcium. The regulation of mitogen-related hepatocyte proliferati on by K-ATP channels advances our insights into liver growth control. The f indings have implications in mechanisms concerning liver development, regen eration, and oncogenesis.