Objective: To study the selective dilatation effects of iptakalim (Ipt) on basilar and pulmonary arterioles, and endothelial cell function of these arterioles in hypoxic rats.
Methods: SD male rats were divided into 2 groups:control and hypoxic group fed in normobaric hypoxic environment (O2 7.8%, 8 h). Arteriole rings about (204 + 5) pm were isolated and the tension of hypoxic arterioles pre-contracted by 6 nmol/L endothelin-1 (ET-1) was observed with wire myograph system model (DMT 610 m). The relaxing response of hypoxic arterioles induced by different concentration of Ipt were detected and endothelial activity was also tested by acetylcholine.
Results: 10(5) mol/L acetylcholine (ACh)-mediated vasodilatation of basilar and pulmonary arterioles was greatly reduced in the hypoxic group than those in control group (P < 0.05). Compared with normal group, a novel ATP-sensitive potassium channel opener Ipt at the concentration ranging from 10(-11) mol/L to 10(3) mol/L, caused stronger dose dependent vasodilatation on hypoxic pulmonary arterioles, and there was no significant difference between control and hypoxic basilar arterioles.
Conclusion: The endothelial function of basilar and pulmonary arterioles was damaged under hypoxic state, and Ipt selectively increased dilatation effects on hypoxic pulmonary arterioles, but not on hypoxic basilar arterioles which could improve high altitude pulmonary edema pathological state and be the novel drug in the treatment of pulmonary hypertension.