Single Ca channel currents in mouse pancreatic B-cells

Barium currents flowing through single Ca²⁺ channels were recorded from outside-out patches isolated from mouse pancreatic B-cells. Only one type of Ca²⁺ channel was observed. In 110 mM Ba²⁺, the single channel conductance was 24 pS (at negative membrane potentials) and the current amplitude at 0 mV was–0.7 pA. Channel openings were activated by depolarisations more positive than –30 mV and showed little inactivation during 200 ms pulses. Open times were increased by BAY K 8644 an decreased by micromolar Cd²⁺. Channel activity was subject to rundown in excised patches and little activity remained after 10 min. These properties resemble those of L-type Ca²⁺ channels in other tissues. It is suggested that this Ca²⁺ channel participates in the generation of the B-cell action potential and mediates the increase in Ca²⁺ influx required for insulin secretion.