The contribution of nitric oxide on the relaxation effects of diethylstilbestrol.

Objective: To evaluate the contribution of nitric oxide NO on the relaxation effects of diethylstilbestrol on rat uterus.

Methods: Uterine rings from 8 nonpregnant Wistar Albino rats 300-350 g in the pro-estrous phase were suspended in an organ bath and electrical field stimulation applied for recording isometric tension. The influence of NO on contractile responses of rat uterine rings was investigated. The effects of NO precursor L-arginine (10(-7) - 10(-4)M) concentration and NO synthase inhibitor L-nitro-arginine-methyl ester (10(-7) - 10(-4)M) concentration and a combination of them on contractile responses were studied in the presence and absence of diethylstilbestrol (2 x 10(-4)M) concentration. The study was carried out at the Department of Pharmacology Laboratory, Faculty of Medicine, Dicle University, Diyarbakir, Turkey.

Results: Totally, 30 samples were investigated n=6 for each group, 5 groups. Diethylstilbestrol inhibited contractile responses 64.2+/- 4.5% n=6, p<0.05. Contractile responses decreased in the presence of L-arginine n=6, p<0.05 and this inhibition was abolished in the presence of L-nitro-arginine-methyl ester n=6, p<0.05. The inhibition on contractile responses to diethylstilbestrol was potentiated in the presence of L-arginine under similar conditions n=6, p<0.05. The contractile responses to electrical field stimulation in the presence of diethylstilbestrol were not affected by L-nitro-arginine-methyl ester n=6, p>0.05.

Conclusion: These data provide evidence that NO may potentiate the inhibitory effects of diethylstilbestrol by different mechanisms on the electrically induced contractions of the non-pregnant rat uterus.