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The effects of endometrium on metabolism of [3H]-arachidonic acid ([3H]-AA) by bovine blastocysts recovered on day 19 postmating were studied in vitro. Blastocysts (n = 12) and endometrial slices were assigned to four incubation groups. In group 1, blastocysts were incubated alone; group 2, endometrial slices were incubated alone; group 3, blastocysts were incubated with endometrial slices; group 4, blastocysts were incubated in 7.5 ml fresh incubation medium plus 7.5 ml frozen-thawed medium from endometrial incubations. In all groups, tissues were incubated in 15 ml modified minimum essential medium (MEM) containing 5 μCi of [3H]-AA and 200 μg radioinert arachidonic acid for 24 h at 37°C in an atmosphere of 50% N2:45% O2:5% CO2. For incubation controls, 5 μCi of [3H]-AA were added to 15 ml MEM and incubated at the same time as tissues from each cow. To evaluate metabolism of [3H]-AA, [3H]-AA and its metabolites were extracted from aliquots of MEM and separated on columns of Sephadex LH-20. Most (78.3 ± 3.2%) of the radioactivity (dpm) in the incubation controls was recovered as [3H]-AA, indicating that there was little breakdown of [3H]-AA in the absence of tissue. Blastocysts produced compounds that migrated with [3H]-13,14-dihydro-15-keto-PGF2α ([2H]-PGFM), [3H]-PGE2 and [3H]-PGF2α. Endometrial slices metabolized very little of the [3H]-AA. Data from groups 1 and 4 were combined (group 14) for analysis because the distribution of dpm did not differ between the two groups. In group 3, blastocysts and endometrial slices incubated together tended(P |
