2 TYPES OF CA CHANNEL IN RAT PANCREATIC BETA-CELLS

Ba currents flowing through single Ca-channels were recorded from cell-attached patches on rat pancreatic ß-cells. Two types of voltage-activated Ca-channels were found. The first (T-type) had a single channel conductance of 8 pS in 100 mM Ba, was activated at a low threshold (around ±50mV) and inactivated by holding potentials positive to ±40 mV. These properties are similar to those described for T-type channels in other preparations. The second type of Ca-channel (L-type) had a single channel conductance of 20pS in 100 mM Ba, was activated at a higher threshold (> ±30mV), showed little inactivation during a 250 ms pulse and could be activated from a holding potential of ±40mV. The dihydropyridine agonist BAYK 8644 selectively prolonged L-type Ca-channel openings. These properties are characteristic of L-type Ca-channels. © 1990 Springer-Verlag.