Objective To study the effects of simulated weightlessness on eNOS expression in the pulmonary artery in rat, and to investigate the mechanism of changed reactivity of pulmonary artery during simulated weightlessness. Methods The experiments were conducted in 16 male Wistar rats, and they were divided into 2 groups: suspension group and control group, 8 rats for each. Tail-suspension (-30?) was carried out for 14d to simulate weightlessness. eNOS protein expression and NO content in pulmonary artery were determined using Western blot analysis and nitrate enzyme-reduction method, respectively. Results Compared with control group, eNOS expression in the rat pulmonary artery increased significantly during simulated weigtlessness. The relative optical density as a result of scanning was 247?2.60, and that of the control was 141?1.72. There were significant differences between the two groups (P

Ojective To study the endothelial mechanism of simulated weightlessness on the reactivity of pulmonary artery. Methods Experiments were conducted using 32 Wistar male rats, which were randomly divided into 2 groups: tail-suspended group and control group, 16 rats for each group. Tail-suspension for 14 days was used to simulate the effects of microgravity. The changes in responses of pulmonary artery to several vascular active agents were determined by using in vitro vessel rings perfusion technique. And the changes were determined again after the endothelium of pulmonary artery was removed. Results Compared with the control group, the contractile responses of pulmonary artery to potassium chloride (68mmol/L) and phenylephrine (PE, 10 -7 ~10 -5 mmol/L) were markedly diminished after 14 days tail-suspension, while the dilatory responses to acetylcholine (Ach, 10 -8 ~10 -6 mmol/L) were markedly enhanced. The vascular reactivity of endothelium-removed pulmonary artery rings to PE and sodium nitroprusside (SNP) did not change after 14 days tail-suspension. Conclusion The contractile responsiveness is attenuated and the dilatory responsiveness is enhanced in the rats' pulmonary arteries after simulated weightlessness. That the pulmonary artery endothelium changes in structure or function after simulated weightlessness might be an important cause of changing in the reactivity of pulmonary artery.

Objective To investigate the effects of dexamethasone on prevention of apoptosis in pulmonary tissues of rats after simulated weightlessness. Methods Tail suspension was used to simulate weightlessness. Thirty Sprague-Dawley male rats were divided randomly into 3 groups: control group, tail suspension for 7 days group, and dexamethasone treatment after suspension group. TUNEL technique was used to detect cell apoptosis in pulmonary tissues. Results The rate of apoptotic cells in the lung of rats suspended for 7 day was higher than that of control group(P

Objective To investigate the effects of dexamethasone on inducible nitric oxide synthase (iNOS) in pulmonary tissues of tail-suspended rats simulating weightlessness. Methods Twenty Sprague-Dawley male rats were randomly divided into 2 groups: tail-suspended for 7 days (n=10) without treatment and dexamethasone treatment group (n=10). Tail-suspension was used to simulate weightlessness. The expression of iNOS in the pulmonary tissue was examined by Western blot and immunohistochemistry. Results The results showed that the level of iNOS in the pulmonary tissue of treatment group was decreased significantly(P