In NG 108-15 cells, bradykinin (BK) activates a potassium current (IK,BK) and inhibits the voltage-dependent calcium current (ICa,V). BK also stimulates a phosphatidylinositol-specific phospholipase C (PI-PLC). The subsequent release of inositol 1,4,5-trisphosphate and increase in intracellular calcium contribute to IK,BK, through activation of a calcium-dependent potassium current. In membranes from these cells, stimulation of PI-PLC by BK is mediated by Gq and/or G11 two homologous, pertussis toxin-insensitive G proteins. Here, we have investigated the role of Gq/l1 in the electrical responses to BK. GTPγS mimicked and occluded both actions of BK, and both effects were insensitive to pertussis toxin. Perfusion of an anti-Gq/11α antibody into the pipette suppressed IK,BK, but not the inhibition of ICa,V by BK. Thus, BK couples to IK,BK via Gq/11, but coupling to ICa,V is most likely via a different, pertussis toxin-insensitive G protein.
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