Low‐conductance high selective inositol (1,4,5)‐trisphosphate activated Ca2+channels in plasma membrane of A431 carcinoma cells

In many cells, activation of receptors coupled to PIP2turnover results in Ca2+release from the intracellular stores accompanied by Ca2+influx across the PM. It is not well established yet whether Ca2+influx is activated by IP3or by an unknown signal generated upon Ca2+store depletion. We report here a single‐channel study of low‐conductance IP3‐activated channels of very high selectivity for Ca2+in the PM of A431 carcinoma cells. The channels are strongly potential dependent and sensitive to [Ca2+]iwithin the physiological range. The data obtained argues for IP3acting directly on plasma membrane Ca2+channels.