Dual effects of nitric oxide in functional and regressing rat corpus luteum

The present study investigated the effect of nitric oxide (NO) on the lifespan of the corpus luteum (CL). Using a competitive nitric oxide synthase (NOS) inhibitor, L-nitro arginine methyl ester (L-NAME, 600 micromol/l), and a long-life NO donor, diethyl-aminetriamine (DETA-NONOate, 10(-8), 10(-6) or 10(-4) mol/l), we found that in ovaries from rats at the mid stage of CL development, endogenous NO increased both glutathione (GSH) and progesterone production. However, during prostaglandin F(2 alpha) (PGF(2 alpha))-induced luteolysis NO acted as an intermediary molecule in the inhibitory effect of PGF(2 alpha), on GSH content. This was supported by the fact that in-vivo PGF(2 alpha) treatment enhanced nitric oxide synthase (NOS) activity. These results indicate that the NO could act with a dual action (protective or pro-oxidant) in CL development.