Expression Of HO In Corpus Cavernosum Of Castrated Rats

objective: Penile erection is the effect of concordant contraction and relaxation of corpus cavernosum smooth muscle, many studies certify that androgen can adjust the contraction and relaxation of corpus cavernosum smooth muscle. Nitric oxide(NO) is the principal non-adrenergic non-cholinergic(NANC) neurotransmitter which mediates penile erection, many literatures concern about that androgen regulates the activity of nitric oxide synthase(NOS) in penie tissue but the results is diversity. NO and carbon monoxide(CO) are all NANC neurotransmitter and have the similar mechanism of action. Heme oxygenase(HO) is the key enzyme that catalysis the generation of endogenous CO, research finds that the contents of CO in corpus cavernosum of castrated rats are significant cutting down ,androgen substitution can reverse this situation, this indicates that androgen can regulate the activity of HO. This study design to determine the diversity expression of HO-1,HO-2 protein and mRNA and nNOS mRNA in corpus cavernosum of castrated rats ,to investigate the mechanism of androgen in erectile dysfunction(ED). Methods:Forty male Sprague-Dawley rats of 10 weeks were randomly divided into:sham-operated 2 weeks group(A group), sham-operated 4 weeks group(B group),2 weeks castrated group(C group),4 weeks castrated group(D group),intraperitoneal anesthesia by 1% pentobarbital,C,D group were castrated by ectomizing bilateral testis and epididymis,A,B group only cut open scrotum but not to disciss testis and epididymis.Rats were raise to the 2nd week and 4th week after operation,drawing blood to detect the serum testosterone level of each group rats by radioimmunoassay,the expression level of HO protein was determined by immunohistochemistry in corpus cavernosum of each group rats,the mRNA expression level of HO and nNOS gene were assayed by RT-PCR.Results:The mean serum testosterone level in group A was 283.222±117.171ng/dl,289.280±87.413ng/dl in group B,7.118±3.7ng/dl in group C,48.826±19.477ng/dl in group D,the serum testosterone level was significantly decreased in castrated group comparing with sham-operated group,one-way analysis of variance(ANOVA) indicated that the serum testosterone level in group C was decreased comparing with group A,and in group D compared with group B(P<0.01),The immunohistochemistry results manifested: HO-1,HO-2 mainly expressed in cytoplasm and cytoblast of corpus cavernosum smooth muscle and vascular endothelial cell,and also in blood sinus endothelial cell and sinus smooth muscle cell,positive staining was brown of cytoplasm and cytoblast. Using integral optical density(IOD) value to analysis the experiment data of immunohistochemistry,the expression of HO-1 protein decreases in group C,D, IOD value in group A,C were 70.25±10.16 and 17.15±9.26(P<0.01), 72.35±9.87 and 28.16±12.27(P<0.01) in group B,D. The expression of HO-2 protein decreased in group C,D, IOD value in group A,C were 176.58±7.36 and 90.58±8.11(P<0.01),177.28±7.79 and 89.31±7.98(P<0.01) in group B,D. The relative mean grey level ratio of nNOS gene in group A was 1.254±0.371,in group B was 1.199±0.214, 0.403±0.143 in group C and 0.783±0.09 in group D,the results of one-way ANOVA indicated that the expression of nNOS gene mRNA decreased in group C compared with group A(P﹤0.01),group D decreased compared with group B(P﹤0.01). The relative mean grey level ratio of HO-1 gene in group A was 1.047±0.07,in group B was 1.006±0.065, 0.537±0.3 in group C and 0.717±0.208 in group D,the mRNA expression of HO-1 gene decreased in group C comparing with group A(P﹤0.01),group D decreased comparing with group B(P﹤0.01). The relative mean grey level ratio of HO-2 gene in group A was 0.54±0.216,in group B was 0.582±0.133, 0.439±0.143 in group C and 0.428±0.116 in group D,the mRNA expression of HO-2 gene decreased in group C comparing with group A(P﹤0.05),group D decreased comparing with group B(P﹤0.01).Conclusion: Androgen deficiency would result in down regulation of expression of HO protein in corpus cavernosum of rats. Androgen deficiency would decrease the expression of HO and nNOS mRNA in corpus cavernosum of rats. Androgen may partly regulate penile erection by HO/CO system.