Hypotonic shock evokes opening of Ca2+-activated K channels in opossum kidney cells.

Using the patch clamp technique we show that exposure of opossum kidney cells to hypotonic shock evokes an outward rectifying potassium current. The corresponding single channel slope conductance approaches 15 pS at depolarizing voltages. The K current also becomes activated after addition of the ionophore A23187 to an isotonic bath medium containing Ca2+. We therefore conclude that the K selective channels are modulated by an elevation of cytoplasmic Ca2+. Evidence is presented that release of Ca2+ from internal stores is involved.