Objective To evaluate the role of angiotensin Ⅱ(AngⅡ) signal passway on the expression of Rho GDP dissociation inhibitor alpha (RhoGDIα) in hypertensive rats. Methods Protein and mRNA expressions of RhoGDIα in aortae of 4, 12 and 18 weekold spontaneously hypertensive rats (SHR, EM>n/EM>= 4) and Wistar Kyoto rats (WKY, EM>n/EM>= 4) were examined by Western blotting and realtime PCR. Aortas from SHR and WKY were analyzed using immonuchemical staining to locate the RhoGDIα in the aorta. The RhoGDIα expression in aorta of hypertensive rat model of aorta coarctation (ACR, EM>n/EM>= 6) was also analyzed using Western blotting. Furthermore, The effect of mechanical strain at 10 % elongation on expression of RhoGDIα in vascular smooth muscle cells (VSMCs) in the presence or absence of L-158809, an antagonist for AngⅡ type 1 receptor, was also evaluated by Western blotting. Results No significant difference of RhoGDIα expression was found between SHR and WKY at 4week-old and 12-week-old. However, in 18-week-old group, RhoGDIα was significantly highly expressed in SHR than that of WKY at both mRNA and protein levels. RhoGDIα was located in the media of the aorta. Expression of RhoGDIα protein was upregulated in aortas of ACR at 2 and 4 weeks as compared with the cont