[Role of C-type natriuretic peptide receptor and large-conductance calcium-activated potassium channels in brain natriuretic peptide-induced porcine coronary artery dilation].

OBJECTIVE: To investigate the role of C-type natriuretic peptide receptor (NPR-C) and large-conductance calcium-activated potassium channels (BK(Ca)) in brain natriuretic peptide (BNP) induced porcine coronary artery dilation. METHODS: Porcine coronary artery rings were obtained and treated with BNP (10(-6) mol/L), BNP + NPR-C antagonist cANF4-28 (10(-6) mol/L) and BNP + BK(Ca) blocker tetraethylammonium (TEA, 1 mmol/L). The vascular tone experiments were observed on 10 vessel segments. BK(Ca) current density was measured by the whole-cell patch clamp technique. RESULTS: The maximum diastolic rate was similar between BNP group (68.51% ± 11.50%) and cANF4-28 + BNP group (65.67% ± 11.90%, P > 0.05) while significantly reduced in TEA + BNP group (28.87% ± 4.55%, all P < 0.05). When the holding potential was set at +60 mV, the BK(Ca) current density of BNP group was (78.48 ± 5.86) pA/pF, which was significantly higher than control group [(53.84 ± 4.55) pA/pF, P < 0.05], which was equally reduced in the TEA group and TEA + BNP group [(28.80 ± 2.76) pA/pF and (30.60 ± 3.88) pA/pF respectively, all P < 0.05 vs. control group]. CONCLUSION: BNP could relax the porcine coronary arterial smooth muscles by increasing BK(Ca) current, and this effect is not mediated by NPR-C.