BK channel blockers inhibit potassium-induced proliferation of human astrocytoma cells

The functional role of BK channels, which are consistently expressed in glioma cells, is not clear. Here we show that the BK channels are regularly active in human I32INI astrocytoma cells at physiological membrane potentials. The proliferation of the cells at the physiological external [K+] of 5 mM is compared with that at the elevated external [K+] of 20 mM, simulating the situation in rapidly growing, necrotic tumours in vivo. High extracellular [K+] in the range 10-30 mM significantly increases the proliferation of I32INI cells. This K+ induced proliferation can be completely abolished by applying the specific BK channel blockers iberiotoxin (IBTX) or I mM tetraethylammonium (TEA). Neither blocker has any effect on cell growth at 5 mM [K+](e). These findings indicate a particular role of BK channels in astrocytoma cell proliferation.