Effect of nitric oxide-induced tyrosine phosphorylation of calcium-activated potassium channel α subunit on vascular hyporesponsiveness in rats

摘要

Objective: To study the effect of nitric oxide-induced tyrosine phosphorylation of large-conductance calcium-activated potassium (BK_(Ca)) channel α subunit on vascular hyporesponsiveness in rats. Methods: A total of 46 Wistar rats of either sex, weighing 250 g ± 20 g, were used in this study. Models of vascular hyporesponsiveness induced by hemorrhagic shock (30 mm Hg for 2 hours) in vivo and by L-arginine in vitro were established respectively. The vascular responsiveness of isolated superior mesenteric arteries to norepinephrine was observed. Tyrosine phosphorylation of BK_(Ca) α subunit was evaluated with methods of immunoprecipitation and Western blotting. Results: In the smooth muscle cells of the superior mesenteric arteries, the expression of BK_(Ca) α subunit tyrosine phosphorylation increased following hemorrhagic shock, and L-arginine could induce BK_(Ca) channel α subunit tyrosine phosphorylation in a time- and dose-dependent manner. L-NAME (Nω-nitro-L-arginine-methyl-ester) , a nitric oxide synthetase inhibitor, could partly restore the decreased vasoresponsiveness of the superior mesenteric arteries after hemorrhagic shock in rats. Down-regulating the protein tyrosine phosphorylation with genistein, a widely-used special protein tyrosine kinase inhibitor, could partly improve the decreased vasoresponsiveness of the superior mesenteric arteries induced by L-arginine in vitro, while up-regulating the protein tyrosine phosphorylation with Na_3VO_4, a protein tyrosine phosphatase inhibitor, could further decrease the nitric oxide-induced vascular hyporesponsiveness, which could be partly ameliorated by 0.1 mmol/L tetrabutylammonium chloride ( TEA ), a selective BK_(Ca) inhibitor at this concentration. Conclusions: Nitric oxide can induce the tyrosine phosphorylation of BK_(Ca) α subunit, which influences the vascular hyporesponsiveness in hemorrhagic shock rats or induced by L-arginine in vitro.