Abstract: Objective To investigate the correlation between the improvement of target organ damage and downregulation of the ratio of connexin 40 in peripheral blood T lymphocyte subsets induced by estrogen intervention in spontaneously hypertensive rats（SHR）. Methods Sixteen to seventeen-week-old male SHR and WKY rats were recruited and randomly divided into three groups:WKY,SHR and estrogen group（n=6,respectively）. After tail artery blood pressure measurement,the basilar artery and renal pathological changes were observed by HE staining;the ratio of CD4⁺/CD8⁺and CD4⁺CD25⁺T cells and the ratio of Cx40 on CD4⁺ and CD8⁺T cells were detected by flow cytometry;the expression of tumor necrosis factor（TNF）-α,interleukin（IL）-6 and IL-10 was detected by enzyme-linked immunosorbent assay（ELISA）. Results HE staining showed that,compared with WKY rats,there were evidently thicken on vascular wall,partly infiltration of inflammatory cell in the blood vessels and glomerular atrophy in SHR,but those phenomena were reversed partly in estrogen group.Compared with WKY rats,the ratio of CD4⁺/CD8⁺was higher（P＜0.05）and the proportion of CD4⁺CD25⁺T cells to CD4⁺cells was lower（P＜0.01）in SHR. However,the ratio of CD4⁺/CD8⁺was descended（P＜0.05）and the proportion of CD4⁺CD25⁺T cells to CD4⁺cells was increased in estrogen group compared with SHR group（P＜0.05）. Compared with WKY rats,the expression of Cx40 on CD4⁺and CD8⁺T cells were higher in SHR（P＜0.01,P＜0.05）. Whereas the expression of Cx40 on CD4⁺and CD8⁺T cells were descended in estrogen group compared with SHR group（P＜0.05）. Moreover,the serum level of IL-6 and TNF-αin SHR were higher than those in WKY rats（P＜0.05,P＜0.01）. And IL-10 was lower in SHR than that in WKY rats（P＜0.01）. After estrogen intervention,the serum level of IL-6 and TNF-αwas decreased（P＜0.05）and IL-10 was increased（P＜0.05）. Conclusion Estrogen could improve the renal and cerebrovascular damage in hypertension,which may be related to the expression of Cx40 in T lymphocytes. The possible mechanism could be that estrogen inhibit the gap junction intercelluar communication and reduce the ralease of inflammatory factors by downregulating the Cx40 in peripheral blood T lymphocyte subsets,and enventually improve the hypertensive target organ damage.