Composition of potassium channels in normal rat coronary smooth muscle cells and activation effects of docosahexaenoic acid

Objective: To investigate the composition of potassium channels in normal rat coronary smooth muscle cells (CASMCs) and the activation effects of flocosahexaenoic acid (DHA). Methods: CASMCs were isolated by enzyme digestion. Effects of different types of potassium channel blockers and/or DHA on potassium channels currents were studied by whole-cell patch clamp technique. Results: Potassium currents were significantly increased with 5 μmol/L DHA perfusion ( P < 0.05 ). The current density was increased from (52.80 ±6. 68) pA/pF to (110.09 ± 13.39) pA/pF (P < 0.05) after DHA perfusion when the stimulation voltage was 100 mV. Compared with baseline, potassium currents were significantly decreased by various inhibitor perfusion (tetraethylammonium: (49.63 ± 5.75 ) pA/pF vs. ( 13.96 ± 2.18 ) pA/pF; ibritoxin: (50.67 ± 7.89) pA/pF vs. (26.53 ± 4.68 ) pA/pF; TRAM-34: (52.60 ± 7.02) pA/pF vs. (46.05 ± 7.60) pA/pF; apamin: (51.97 ± 3.83) pA/pF vs. (44.89 ± 5.04) pA/pF; 4-aminopyridine: (51.19 ±3.44) pA/pF vs. (29.92±2.8l) pA/pF; glyburide: (49.67 ± 1.77 ) pA/pF vs. (49.61 ± 1.87) pA/pF, all P < 0.05 ). In presence of different inhibitors, potassium channel current densities were increased after DHA perfusion except tetraethylammonium (tetraethylammonium: ( 12.79 ± 1.89) pA/pF; ibritoxin: (67.08 ±5.54) pA/pF; TRAM-34; ( 117. 91 ±21.79) pA/pF: apamin: ( 108. 33 +7.06) pA/pF; 4-aminopyridine: (127.73 ± 20.56) pA/pF; glyburide; (121.53 ± 13.83 ) pA/pF, all P < 0.05 compared with baseline ) . Conclusions: Large-conductance calcium-activated potassium channel and voltage-gated potassium channel are the major constituents of potassium channels in CASMCs. DHA can activate potassium channels in CASMCs, mainly the large conductance calcium-activated potassium channel, thus dilate coronary arteries.