tailieunhanh - Báo cáo y học: " Hypoxic pulmonary vasoconstriction: role of voltage-gated potassium channels"

Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học 'Respiratory Research cung cấp cho các bạn kiến thức về ngành y đề tài: " Hypoxic pulmonary vasoconstriction: role of voltage-gated potassium channels. | http content 1 1 040 Review Hypoxic pulmonary vasoconstriction role of voltage-gated potassium channels Michèle Sweeney and Jason X-J Yuan University of California San Diego California USA Received 19 May 2000 Revisions requested 8 June 2000 Revisions received 15 June 2000 Accepted 15 June 2000 Published 3 July 2000 Respir Res 2000 1 40-48 Current Science Ltd Print ISSN 1465-9921 Online ISSN 1465-993X Abstract Activity of voltage-gated potassium Kv channels controls membrane potential which subsequently regulates cytoplasmic free calcium concentration Ca2 cyt in pulmonary artery smooth muscle cells PASMCs . Acute hypoxia inhibits Kv channel function in PASMCs inducing membrane depolarization and a rise in Ca2 cyt that triggers vasoconstriction. Prolonged hypoxia inhibits expression of Kv channels and reduces Kv channel currents in PASMCs. The consequent membrane depolarization raises Ca2 cyt thus stimulating PASMC proliferation. The present review discusses recent evidence for the involvement of Kv channels in initiation of hypoxic pulmonary vasoconstriction and in chronic hypoxia-induced pulmonary hypertension. Keywords hypoxia intracellular calcium membrane potential smooth muscle Introduction The main function of the low-pressure low-resistance pulmonary circulation is to oxygenate blood to be supplied to the rest of the body. In order to perform this function efficiently the lung must match its regional ventilation and perfusion. Thus in regions where alveolar oxygen levels are low the pulmonary arteries constrict diverting blood flow to better ventilated areas of the lung where gas exchange can take place more efficiently. This important physiologic phenomenon is known as hypoxic pulmonary vasoconstriction HPV and is unique to the pulmonary circulation hypoxia generally causes dilatation in systemic arterial beds. In the fetus gas exchange occurs via the placenta and HPV acts to maintain a high pulmonary vascular resistance to divert .