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 produce prostaglandins and if prostaglandins may have a role in the shedding of the zona pellucida, i.e., embryo hatching. For Experiment 1, embryos were collected on day (d) 4, 8, 10, 12 or 14 of pregnancy and incubated with 1 microCi of [14C] arachidonic acid (AA) for 24 h. Based upon high-performance liquid chromatography, embryos from all days converted AA to a number of compounds; the amounts produced differed with day. Primarily, embryos produced an unidentified polar compound, 6-keto-PGF1 alpha, PGF2 alpha, PGE2, 13,14-dihydro-15-keto-PGF2 alpha and PGB2. For Experiment 2, embryos collected on d 7 of pregnancy were incubated for a maximum of 6 d in 500 microL of medium containing either ethanol (control; 20 microL), indomethacin (INDO; 10(-4) M), PGE2 (2 ng) or INDO (10(-4) M) + PGE2 (2 ng). Embryos were evaluated daily for hatching from the zona pellucida. The hatching rates (percentage) for control, INDO, 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 rate for embryos treated with PGE2 alone was greater (P < .05) than that for embryos in any group with INDO. The results indicate that early ovine embryos can convert AA to various compounds in vitro, and prostaglandins may have a role in the hatching of sheep embryos from the zona pellucida.