Role of potassium channels in the regulation of intracellular free Ca~(2+) concentration of pulmonary artery smooth muscle cells in rats

AIM: To investigate the role of potassium channels in the regulation of intracellular free calcium concentration (_i) of pulmonary artery smooth muscle cells (PASMCs) in rats. METHODS: The fluorescence Ca 2+ indicator Fura-2/AM was used to observe _i of rat PASMCs in normal and chronic hypoxic condition. The influences of potassium channels on PASMCs proliferation were assessed by MTT assay. RESULTS: 1. In normoxic condition,_i was (156.91±8.60) nmol/L,and in hypoxic condition,_i was (294.01±16.81) nmol/L. 2. In normoxic condition,the voltage-dependent K +-channel antagonist 4-aminopyridine (4AP),but not the Ca 2+ -activated K +-channel antagonist tetraethylammonium (TEA) and the ATP-sensitive K +-channel antagonist glibenclamide (Glib) increased _i. 3. In hypoxic condition,4AP and TEA caused the rise in _i [(422.41±24.28) nmol/L,(380.84±11.02) nmol/L,respectively],but Glib had no effect on _i. 4. MTT assay showed that 4AP increased the value of absorbing light degree ( A value) in normoxic and hypoxic condition (0.582±0.062,0.873±0.043,respectively, P 0.01),TEA increased A value only in hypoxic condition,and Glib had no effect on the proliferation of PASMCs. CONCLUSIONS: K_V plays an important role in the regulation of _i and proliferation of PASMCs. K_ Ca serves as distinct responsive roles in the regulation of proliferation of PASMCs in hypoxic condition. K_ ATP has no effect on _i and proliferation of PASMCs in normoxic and hypoxic conditions.