ABSTRACT
Objective To observe the effects of intermittent 45? head-uptilt on endothelin(ET-1) expression and morphological changes of femoral and carotid arteries in rabbits induced by 21 d simulated weightlessness.Method Twenty-four healthy male rabbits were randomly divided into control group,simulated weightlessness group and countermeasure group,8 rabbits in each group.The simulated weightlessness group kept head-down tilt for 21 d.The countermeasure group was exposed to 45? head-up tilt for 2 h every day during 21 d head-down tilt.After 21 d experiment,structure of femoral artery and carotid artery were studied and ET-1 expression was tested by immunohistochemical method.Result Detachment of endothelial cells in femoral artery,necrosis of smooth muscle cells and decreased ET-1 expression were found in animals in the simulated weightlessness group,and the vessel wall became thinner.While hyperplasia of endothelial cells and thickened internal elastic lamina of the carotid artery were also observed.No significant changes were observed in femoral artery and carotid artery in animals of the countermeasure group.ET-1 expression decreased in femoral artery but increased in carotid artery in animals of the simulated weightlessness group,but no significant change was found in both femoral and carotid arteries in animals of the countermeasure group as compared with those in the control group.Conclusion Twenty-one days simulated weightlessness may induce an atrophic change and decreased ET-1 expression in femoral artery,and hyperplastic change and increased ET-1 expression in carotid artery in rabbits.Two-hour 45? head-up tilt every day may partly counteract the change in femoral artery and carotid artery induced by simulated weightlessness.