Effects of ethanol on intraovarian nitric oxide production in the prepubertal rat

Nitric oxide (NO) has been shown to contribute to ovarian development and f unction. In non-ovarian tissues NO can be altered by ethanol (ETOH), a drug considered to be a gonadal toxin in men as well as male and female rats. T he present study was undertaken to determine if some of the detrimental eff ects of chronic ETOH exposure on prepubertal ovarian function could be due to ETOH-induced alterations in the intraovarian NO system. Rats were implan ted with intragastric cannulae on day 24 and began receiving control or ETO H diets on day 29. AU rats were killed on day 34, determined to be in the l ate juvenile stage of development, and their ovaries and blood were collect ed. We analyzed the expression of the two constitutive forms of nitric oxid e synthase (NOS), i.e. neuronal (n) NOS and endothelial (e) NOS, as well as the inducible (i) form of NOS protein in the ovaries of control and ETOH-t reated rats by Western immunoblotting. Results demonstrate that eNOS protei n increased markedly (P<0.02; 140 kDa) in ETOH-treated rats compared with c ontrols. ETOH treatment did not alter the protein expression of nNOS (155 k Da) and only slightly increased that of iNOS (130 kDa). We also assessed NO S activity as determined by nitrite accumulation and by the conversion of L -[C-14]arginine to L-[C-14]citrulline. In this regard, the ETOH-treated ani mals showed an increase in ovarian nitrite generation (P<0.05), as well as an increase in ovarian citrulline formation (P<0.0001), when compared with control animals. Along with the above described ETOH-induced increases in o varian eNOS and NO activity, the serum levels of estradiol were concomitant ly suppressed (P<0.001) in the ETOH-treated rats. These results demonstrate for the first time the ETOH-induced changes in the prepubertal ovarian NO/ NOS system, and suggest that these alterations contribute to the detrimenta l actions of the drug on prepubertal ovarian development and function.