Effects of L-Arginine and L-Omega-Nitro-L-Arginine Methyl Ester on Fertility of Female Rats

Nitric oxice (NO) is produced by the action of nitric oxide synthase (NOS) on L-arginine. This study examined the effect of stimulating and inhibiting NOS activity with L-arginine and L-omega-nitro-L-arginine methyl ester (L-NAME), respectively, on female rat fertility. Female rats received peritoneal injections of L-arginine, L-NAME or saline for two weeks and the effect on fertility was evaluated by determining the number of pregnancies, implantation sites per dam, fetal viability and embryonic resorptions. Stimulation of NOS activity significantly decreased pregnancy rates and increased embryolethality, with significant decreases in the weights of the ovaries and uteri. Inhibition of NOS activity had no signifcant effect on the pregnancy outcomes, but increased embryolethality relative to the implantation sites per dam. Furthermore, ovary weights were significantly greater and uterus weights significantly less than the controls. Thus, optimal levels of NO are important for gravidity, proper functioning of the endometrium, as well as, embryonic implantation.