OBJECTIVETo analyze the changes of heme oxygenase-1 (HO-1) and heme oxygenase-2 (HO-2) in the vaginal smooth muscle of ovariectomized female rats and to investigate the effects of estrogen on the expressions of HO-1 and HO-2 in the vaginal smooth muscle.

METHODSTwenty-four 8-week old female SD rats were equally randomized into Group A (2-week castrated) , B (4-week castrated), C (2-week sham operation) and D (4-week sham operation). The levels of plasma estradiol were measured by radio-immunoassay for all the rats and the expressions of HO-1 and HO-2 in the vaginal muscle were detected and analyzed by immunohistochemistry and RT-PCR.

RESULTSThe postoperative level of plasma estradiol was significantly lower in Groups A and B than in C and D (P < 0.05). And the expressions of HO-1 and HO-2 in the vaginal smooth muscle were significantly decreased in the first two groups as compared with the latter two.

CONCLUSIONHO-1 and HO-2 are expressed in the vaginal smooth muscle of the female rats, and their decreased expressions are correlated with the lowered level of plasma estradiol. Estrogen may play a physiological role in the vaginal smooth muscle via HO/CO.