Regional specificity of adaptation change in large elastic arteries of simulated microgravity rats

This study was designed to test the hypothesis that a medium-term simulated microgravity by tail-suspension (SUS) induces hypertrophic and atrophic changes in the common carotid artery and abdominal aorta with their innermost smooth muscle (SM) layers being most profoundly affected. The second purpose was to elucidate whether vascular local renin-angiotensin system (L-RAS) plays an important role in the differential remodeling of the two kinds of large arteries by examining the gene and protein expression of angiotensinogen (AO) and angiotensin II receptor type 1 (AT1R) and their localization in the vessel wall. The results showed that SUS induced an increase in the media thickness of the common carotid artery due to hypertrophy of the four SM layers and a decrease in the total cross-sectional area of the nine SM layers of the abdominal aorta without significant change in its media thickness. Irrespective of the nature of remodeling, the most prominent changes were in the innermost layers. Immunohistochemistry, in situ hybridization, Western blot, and real time quantitative PCR analysis revealed that SUS induced an up- and down-regulation in AO and AT1R expression in the common carotid artery and abdominal aorta, respectively. In conclusion, our findings have demonstrated some special features in the structural adaptation of large elastic arteries due to a medium-term simulated microgravity.