Dual effects of tetrandrine on calcium-activated potassium channels in pulmonary artery smooth muscle cells

ATM: To study the effects of tetrandrine (Tet) on calcium-activated potassi um channels. METHODS: Inside-out configuration of patch-clamp single channe l recording techniques. RESULTS: Tet 7.5 and 15 mu mol.L-1 increased the op en probability from control value 0.251 +/- 0.012 to 0.340 +/- 0.013 and 0. 415 +/- 0.011, respectively (P < 0.01), decreased the close time from (61 /- 15) ms to (33 +/-: 10) and (28 +/- 11) ms, respectively (P < 0.01). But Tet 30 mu mol.L-1 decreased the open probability and open time to (0.114 +/ - 0.008) and (1.47 +/- 0.09) ms, respectively [P < 0.01 vs control (0.251 /- 0.012) and (20 +/- 8) ms]. CONCLUSION: Tet has concentration-dependent d ual effects on K-Ca channels in isolated rat pulmonary smooth muscle cells.