[Role of nitric oxide in the synthesis of prostaglandin F2 alpha and progesterone during luteolysis in the rat].

In the corpus luteum (CL) prostaglandin F2 alpha (PGF2 alpha) is a luteolytic agent. Nitric oxide (NO) is a messenger molecule capable of modulating diverse pathophysiological processes. Many of these functions are related with the female reproductive tract. The aim of the present study was to investigate the role of ovarian NO in PGF2 alpha production arid in progesterone synthesis during CL regression in the rat. By means of the intrabursa (i.b.) ovarian sac treatment of two competitive NO inhibitors, NG-monomethyl-L-arginine (L-NMMA; 1 mg/kg); NW-Nitro-L-arginine methyl ester (L-NAME, 3 mg/kg) and sodium nitroprusside (SNP, 0.05 mg/kg) as a NO generator we found that NO, produced by the ovarian tissue during the last days (days 8 and 9) of CL development, acted by increasing PGF2 alpha production in the ovary and diminishing seric progesterone levels leading to CL involution. We also postulated a positive feedback mechanism between PGF2 alpha and NO, to ensure luteal regression. Thus, we injected intraperitoneally (i.p.) a luteolytic dose (3 micrograms/kg) of a synthetic PGF2 alpha during the mid and late phase of CL development. The ovarian activity was evaluated. The results confirmed our hypothesis; we did not see any effect in mid-stage of CL development, while at a late stage enhancement of ovarian NOs activity was observed in PGF2 alpha-infected animals.