[Effects of docosahexaenoic acid on ion channels of rat coronary artery smooth muscle cells].

Objective: To investigate the effects of docosahexaenoic acid (DHA) on large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels and voltage-dependent K(+) (K(V)) channels in rat coronary artery smooth muscle cells (CASMCs), and evaluate the vasorelaxation mechanisms of DHA.

Methods: BK(Ca) and K(V) currents in individual CASMC were recorded by patch-clamp technique in whole-cell configuration. Effects of DHA at various concentrations (0, 10, 20, 40, 60 and 80 µmol/L) on BK(Ca) and K(V) channels were observed.

Results: (1) DHA enhanced IBK(Ca) and BK(Ca) tail currents in a concentration-dependent manner while did not affect the stably activated curves of IBK(Ca). IBK(Ca) current densities were (68.2 ± 22.8), (72.4 ± 24.5), (120.4 ± 37.9), (237.5 ± 53.2), (323.6 ± 74.8) and (370.6 ± 88.2)pA/pF respectively (P < 0.05, n = 30) with the addition of 0, 10, 20, 40, 60 and 80 µmol/L DHA concentration, and half-effect concentration (EC(50)) of DHA was (36.22 ± 2.17)µmol/L. (2) IK(V) and K(V) tail currents were gradually reduced, stably activated curves of IK(V) were shift to the right, and stably inactivated curves were shifted to the left in the presence of DHA. IK(V) current densities were (43.9 ± 2.3), (43.8 ± 2.3), (42.9 ± 2.0), (32.3 ± 1.9), (11.7 ± 1.5) and (9.6 ± 1.2)pA/pF respectively(P < 0.05, n = 30)post treatment with 0, 10, 20, 40, 60 and 80 µmol/L DHA under manding potential equal to +50 mV, and EC(50) of DHA was (44.19 ± 0.63)µmol/L.

Conclusion: DHA can activate BK(Ca) channels and block K(V) channels in rat CASMCs, the combined effects on BK(Ca) and K(V) channels lead to the vasodilation effects of DHA on vascular smooth muscle cells.