Figure 4.

I_Cl(Ca) decays in the presence of a sustained rise in [Ca²⁺]_i. Exposure to ionomycin resulted in a sustained elevation of [Ca²⁺]_i and activation of I_Cl(Ca) in a cell voltage-clamped at −60 mV (Left). The current completely inactivated, despite the sustained rise in [Ca²⁺]_i. Equivalent experiments were performed in potassium-containing solution, holding at E_Cl (0 mV) to isolate the calcium-activated potassium current (Right). Unlike I_Cl(Ca), the calcium-activated potassium current was sustained as long as [Ca²⁺]_i was elevated.