Nitrendipine is a potent inhibitor of the Ca²⁺-activated K⁺ channel of human erythrocytes

Nitrendipine, a classical blocker of L-type Ca²⁺ channels, is shown to be a potent inhibitor of the Ca²⁺-activated K⁺ channel of human erythrocytes. In erythrocytes suspended in a solution with physiological Na⁺ and K⁺ concentrations and in which the channel was activated using the Ca²⁺ ionophore ionomycin, nitrendipene inhibited K⁺(⁸⁰Rb⁺) influx with an I₅₀ of around 130 nM. Similar results were obtained for K⁺(⁸⁰Rb⁺) efflux, and for K⁺(⁸⁰Rb⁺) influx into cells suspended in a high-K⁺ medium.