ARACHIDONIC-ACID METABOLISM DURING EARLY DEVELOPMENT OF OVINE EMBRYOS- A POSSIBLE RELATIONSHIP TO SHEDDING OF THE ZONA-PELLUCIDA

Two experiments were conducted to determine if early ovine embryos pro duce prostaglandins and if prostaglandins may have a role in the shedd ing of the zona pellucida, i.e., embryo hatching. For Experiment 1, em bryos were collected on day (d) 4, 8, 10, 12 or 14 of pregnancy and in cubated with 1 muCi of [C-14] arachidonic acid (AA) for 24 h. Based up on high-performance liquid chromatography, embryos from all days conve rted AA to a number of compounds; the amounts produced differed with d ay. Primarily, embryos produced an unidentified polar compound, 6-keto -PGF1alpha, PGF2alpha, PGE2, 13,14-dihydro-15-keto-PGF2alpha and PGB2. For Experiment 2, embryos collected on d 7 of pregnancy were incubate d for a maximum of 6 d in 500 muL of medium containing either ethanol (control; 20 muL), indomethacin (INDO. 10(-4) M), PGE2 (2 ng) or INDO (10(-4) M) + PGE2 (2 ng). Embryos were evaluated daily for hatching fr om the zona pellucida. The hatching rates (percentage) for control, IN DO, PGE2 and INDO + PGE2 were 46.4, 34.5, 60.0, and 30.0, respectively . There was a main effect (P < .09) of treatment, and the hatching rat e for embryos treated with PGE2 alone was greater (P < .05) than that for embryos in any group with INDO. The results indicate that early ov ine embryos can convert AA to various compounds in vitro, and prostagl andins may have a role in the hatching of sheep embryos from the zona pellucida.