Changes in the K+ current-density of MCF-7 cells during progression through the cell cycle: Possible involvement of a h-ether.a-gogo K+ channel

MCF-7 cells express voltage-activated K+ channels. In the present study, we used the patch-clamp and RT-PCR techniques to investigate the involvement of these channels during the cell cycle progression. The outward rectifier current (I-K)ecorded during depolarization was almost completely suppressed by the classical K+ channel blocker tetraethylammonium (TEA) in MCF-7 cell s. TEA also inhibited cell proliferation, as measured with H-3-thymidine in corporation. Moreover, profound changes were observed in both the resting m embrane potential (RMP) and I-K during the release from the G0/G1 phase of the cell cycle. MCF-7 cells arrested in G0/G1 were depolarized (-26.3 +/- 1 0 mV, n = 30) and I-K-density was small (9.4 +/- 5.6 pA/pF, n = 60) compare d to cells progressing in the G1 phase (RMP = -60 +/- 7.9 mV, n = 35 and I- K-density = 30.2 +/- 8.5pA/pF; n = 76). I-K was highly sensitive to Mg2+, a stemizole and TEA (10 mM). Extracellular perfusion of 5 mM Mg2+ dramaticall y slowed the activation and perfusion of 2 muM astemizole inhibited both I- K (20 +/- 3%) and cell proliferation (23%). Moreover, the h-EAG rnRNA expre ssion was modulated during the cell cycle. Thus, these data suggested that h-EAG K+ channels play a role in controlling the proliferation and/or cell cycle.