Inyección de prostaglandina F2 alfa (PGF2α) en el folículo preovulatorio de la yegua

Las prostaglandinas (PGE2 y PGF2α) ejercen un rol esencial en el proceso de la ovulacion en los mamiferos. El objetivo de este experimento fue determinar si la inyeccion intrafolicular con prostaglandina F2 alfa (PGF2α) administrada en el periodo preovulatorio inducia la ovulacion normal y formacion del cuerpo luteo, confirmado mas tarde con la presencia de una vesicula embrionaria. Se utilizaron 6 yeguas mestizas en dos ciclos estrales cada una, con un diseno crossover. El tracto reproductivo de las yeguas fue ecografiado cada 24 h desde el dia 15 del ciclo (Dia 0 = dia de la ovulacion) hasta el momento de la puncion folicular (Hora 0). La puncion ecoguiada del foliculo preovulatorio (diametro ≥ 35mm y presencia de moderado edema uterino) se realizo a traves del flanco, inyectando 750 µg de PGF2α diluido en 0,5 ml de agua esteril (grupo tratado n=6) o placebo (0,5 ml de agua de inyeccion) (grupo control n=6). Previo a la puncion, las yeguas fueron inseminadas con semen fresco. Se obtuvieron imagenes ultrasonograficas cada 12 h del foliculo punzado y se tomaron muestras de sangre cada 48 h de la vena yugular para determinar los niveles plasmaticos de progesterona. Cinco de las seis yeguas (83%) del grupo tratado, tuvieron fallas en la ovulacion y solo una de las yeguas ovulo pero no se obtuvo prenez. De acuerdo con estos resultados, la inyeccion intrafolicular con PGF2α no permitiria la ovulacion normal y, contrariamente a lo esperado, induciria la formacion de foliculos hemorragicos anovulatorios. Ademas, se observo un retraso en la elevacion de progesterona en la unica yegua que ovulo.   Injection of prostaglandin F2 alpha (PGF2α) into the mare’s preovulatory follicle Abstract. Prostaglandins (PGE2 and PGF2α) play an essential role in the ovulation process in mammals. The objective of this experiment was to determine whether intrafolicular injection with prostaglandin F2 alpha (PGF2α) administered in the pre-ovulation period induced normal ovulation and corpus luteum formation, it was later confirmed with the presence of an embryonic vesicle. Six mixed-breed mares were used in two estrous cycles each, with a crossover design. The ultrasonographic examination of the reproductive tract was performed every 24 hours from day 15 of the cycle (Day 0 = day of ovulation) until the time of follicular puncture (Hour 0). The ultrasound guided puncture of the preovulatory follicle (diameter ≥ 35 mm and presence of moderate uterine edema) was performed through the flank, injecting 750 µg of PGF2α diluted in 0.5 ml of sterile water (treated group n = 6) or placebo (0.5 ml of injection water) (control group n = 6). Prior to puncture, the mares were inseminated with fresh semen. Ultrasound images were obtained every 12 h of the punctured follicle and blood samples were taken every 48 h from the jugular vein to determine plasma progesterone levels. Five of the six mares (83%) of the treated group had ovulation failures and only one of the mares ovulated but no pregnancy was obtained. According to these results, intrafolicular injection with PGF2α at the concentration used would not allow normal ovulation and contrary to expectations would induce the formation of anovulatory hemorrhagic follicles. In addition, a delay in progesterone rise was observed in the only mare that ovulated.