Abstract: | Two experiments were conducted to determine the effects of 2-hydroxy-estradiol-17β (2---OH---E2; 0, 50 and 100 μM) and estradiol-17β (E2; 0, 25 and 50 μM) on prostaglandin (PG) E and PGF2α 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 E2 or catechol estrogen treatment. Release of PGF2α into the culture medium decreased (p<0.001) linearly with increasing concentrations of 2---H---E2 in both periods. Release of PGE was not affected by 2---OH---E2, therefore 2---OH---E2 increased (p<0.06) the PGE:PGF2α. When E2 was added to the medium, release of PGE was decreased (p<0.01) during the second and third periods. Release of PGF2α also was decreased (p<0.05) by E2 during period 2, but E2 did not alter the PGE:PGF2α. 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 E2 on the synthesis of PGE and PGF2α. Catechol estrogens and E2 may inhibit PG synthesis and modify the PGE:PGF2α during the establishment of pregnancy in pigs. |