Synthesis of prostaglandins by pig blastocysts cultured in medium containing estradiol or catechol estrogen

Abstract

Two experiments were conducted to determine the effects of 2-hydroxy-estradiol-17 β (2OHE 2; 0, 50 and 100 μM) and estradiol-17 β (E 2; 0, 25 and 50 μM) on prostaglandin (PG) E and PGF 2 α synthesis by day-10 pig blastocysts (day 0 is first day of estrus). Blastocysts were incubated in a modified Krebs-Ringer bicarbonate medium, supplemented with bovine serum albumin (4 mg/ml) and the vitamins and amino acids (essential and nonessential) in Minimum Essential Medium (without phenol red or antibiotics). The incubations were conducted at 39°C for three 2-h periods; the second and third periods included an E 2 or catechol estrogen treatment. Release of PGF 2 α into the culture medium decreased ( p<0.001) linearly with increasing concentrations of 2HE 2 in both periods. Release of PGE was not affected by 2OHE 2, therefore 2OHE 2 increased ( p<0.06) the PGE: PGF 2 α. When E 2 was added to the medium, release of PGE was decreased ( p<0.01) during the second and third periods. Release of PGF 2 α also was decreased ( p<0.05) by E 2 during period 2, but E 2 did not alter the PGE: PGF 2 α. Content of PGs in blastocysts at recovery was less than 10% of the PGs released in vitro. Therefore, these studies demonstrate effects of both the primary and catechol forms of E 2 on the synthesis of PGE and PGF 2 α. Catechol estrogens and E 2 may inhibit PG synthesis and modify the PGE: PGF 2 α during the establishment of pregnancy in pigs.