Studies On The Mechanisms Of Changes In Pulmonary Arterial Responsiveness After Simulated Weightlessness

Post-flight orthostatic intolerance is one of the symptoms experienced by astronauts. Space medicine has been focusing on the mechanism of the phenomena which is not fully clarified so far. Recently, studies showed that the hyporesponsiveness of arterial systems induced by weightlessness was thought to be one of major reasons for post-flight orthostatic intolerance. Pulmonary vascular is an effector of baroreceptor reflex, which can exert significant control of pulmonary resistance and capacitance after orthostatic challenge. Thus changes in the responsiveness of pulmonary artery may significantly alter the loading of heart and predispose to orthostatic intolerance. Objective The purpose of this study is to discuss whether the influence on pulmonary arterial responsiveness induced by simulated weightlessness is related to change in eNOS and HO-1 expression. Method Male Wistar rats tail-suspension(14d) were used to simulated the physiological effects of weightlessness. Vascular rings in vitro bathing technique was used to measure the responses of pulmonary arterial rings to PE, KCL, ACh and SNP from control and 14d tail-suspension rats; Western Blotting technique was used to determine the changes of eNOS and HO-1 expression of pulmonary arterial tissue. Results The contractile response to PE and KCL were significantly lower, and the dilatory responses to ACh was markedly enhanced in pulmonary arterial rings from tail-suspension rats as compared with those of control(P<0.05);The responses of endothelium-removed pulmonary artery rings to PE and SNP did not change between control and tail-suspension rats; In presence of L-NAME, the differential response to PE between control and tail-suspension rats was abolished; Data from Western Blotting showed...