Metabolism of arachidonic acid in vitro by porcine blastocysts and endometrium.

Metabolism of radiolabeled arachidonic acid (*AA) by blastocysts and endometrial slices recovered from five gilts 16 days after detection of estrus was studied in vitro. Blastocysts from each gilt were divided into four 216 +/- 18 mg portions, and each portion was placed into a separate petri dish containing 15 ml modified minimum essential medium (MEM). The incubates from each gilt received either 25, 50, 100 or 200 micrograms radioinert arachidonic acid (AA). Endometrium was dissected from each uterine horn, sliced and duplicate 509 +/- 3 mg portions from each gilt were placed into petri dishes containing 15 ml MEM and 200 micrograms AA. All incubates received 5 microCi of *AA (either [14C]-arachidonic acid or [3H]-arachidonic acid). The incubates were rocked at 37 degrees C for 24 h in an atmosphere of 50% N2:45% O2:5% CO2. After incubation, tissues and MEM were separated by centrifugation. Metabolism of *AA was assessed in extracts of MEM and tissue homogenates by separating *AA and its metabolites on columns of Sephadex LH-20. Blastocysts produced compounds that migrated with [3H]-13,14-dihydro-15-keto-PGF2 alpha (*PGFM), [3H]-PGE2 (*PGE2) and [3H]-PGF2 alpha (*PGF2 alpha). The greatest (P less than .05) proportion (35.7 +/- 1.8%) of the radioactivity in blastocyst MEM was recovered as PGE2. In blastocyst homogenates, most (66.2 +/- 3.3%; P less than .05) of the radioactivity was in a nonpolar peak assumed to be arachidonate esters. The concentration of AA in MEM did not alter metabolism of *AA by blastocysts. Endometrial slices produced *PGFM and *PGE2 but only in small amounts, and they were capable of producing nonpolar, probably esterified, forms of *AA. It was concluded that porcine blastocysts produce and metabolize prostaglandins in vitro and that they make a contribution to the uterine milieu during early pregnancy.