[Molecular mechanisms of androgens regulating the eNOS expression in rat corpus cavernosum]

To investigate whether androgens can regulate the expression of eNOS in rat corpus cavernosum through AKT3, PIK3CA, CALM, and CAV1 and influence erectile function.

Thirty-six 8-week-old male SD rats were randomly divided into groups A (4-week control), B (6-week control), C (4-week castration), D (6-week castration), E (4-week castration + testosterone replacement), and F (6-week castration + testosterone replacement). Both the testis and epididymis were removed from the rats in groups C, D, E and F, and on the second day after surgery, the animals of groups E and F were subcutaneously injected with testosterone propionate at 3 mg per kg of the body weight qd alt while all the others with isodose oil instead. At 4 weeks (for groups A, C and E) and 6 weeks (for groups B, D and F) after treatment, we detected the maximum intracavernous pressure (ICPmax), the mean carotid arterial pressure (MAP) and their ratio (ICPmax/MAP), measured the level of serum testosterone (T), and determined the expressions of eNOS, P-eNOS, AKT3, PIK3CA, CALM and CAV1 in the corpus cavernosum by Western blot and immunohistochemistry.

No statistically significant differences were observed in the body weight and MAP among different groups. The serum T level and ICPmax/MAP were remarkably lower in groups C and D than in the other four groups (P<0.01) as well as in groups E and F than in A and B (P<0.05) but exhibited no significant differences either between E and F or between A and B. Immunohistochemistry showed that eNOS and P-eNOS were mainly expressed in the vascular endothelial cell membrane and cavernous vascular lumen, while AKT3, PIK3CA, CALM and CAV1 chiefly in the vascular endothelial cell cytoplasm and membrane, with a few in the smooth muscle cells. Western blot analysis manifested that the expressions of eNOS, P-eNOS, AKT3, PIK3CA, CALM and CAV1 were markedly lower in groups C and D than in A, B, E and F (P<0.01) as well as in D than in C (P<0.05) but those in groups E and F did not showed any significant difference from those in A and B, nor E from F or A from B.

Androgens can improve erectile function by upregulating the expressions of AKT3, PIK3CA, CALM and CAV1 protein molecules and activating eNOS after its phosphorylation, though the exact molecular mechanisms are yet to be further studied.