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

Nitric oxide (NO) has been shown to contribute to ovarian development and function. 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. The present study was undertaken to determine if some of the detrimental effects of chronic ETOH exposure on prepubertal ovarian function could be due to ETOH-induced alterations in the intraovarian NO system. Rats were implanted with intragastric cannulae on day 24 and began receiving control or ETOH diets on day 29. All rats were killed on day 34, determined to be in the late juvenile stage of development, and their ovaries and blood were collected. We analyzed the expression of the two constitutive forms of nitric oxide 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-treated rats by Western immunoblotting. Results demonstrate that eNOS protein increased markedly (P<0.02; 140 kDa) in ETOH-treated rats compared with controls. ETOH treatment did not alter the protein expression of nNOS (155 kDa) and only slightly increased that of iNOS (130 kDa). We also assessed NOS activity as determined by nitrite accumulation and by the conversion of L-[14C]arginine to L-[14C]citrulline. In this regard, the ETOH-treated animals 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 ovarian eNOS and NO activity, the serum levels of estradiol were concomitantly 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 detrimental actions of the drug on prepubertal ovarian development and function.