Production of Steroids and Release of Prostaglandins by Spherical Pig Blastocysts in vitro

Abstract

Levels of pregnenolone and progesterone in spherical pig blastocysts (near 4 and 15 /lM respectively) exceeded respective levels in histotroph by about 400-fold. When blastocysts were cultured for 5 days in a synthetic medium containing pregnenolone sulfate (l /lM), daily rates of release of pregnenolone, progesterone, androstenedione, testosterone, oestrone and oestradiol were determined to be near 320, 45, 2.6, 27, O' 8 and 9· 2 fmol per blastocyst respectively. Daily outputs of progesterone and testosterone (fmol per blastocyst) diminished (P < O' 05) to l' 3 and undetectable levels « 2) respectively in the presence of Trilostane (94 /lM). Increasing the content of pregnenolone sulfate in the culture medium (to 4·5 /lM) resulted in higher daily rates of release of pregnenolone and progesterone (to near 1740 and 380 fmol per blastocyst respectively), verifying activity of 3i1-hydroxy-Ll5-steroid dehydrogenase, and of arylsulfatase, in tissues of intact spherical pig blastocysts. Prostaglandin E2 was the predominant prostaglandin (PG) released by cultured blastocysts (about 1 fmol per blastocyst per hour), hourly rates of release of PGH2 (derived) and PGF2" being near 0·1 and <0·06 fmol per blastocyst respectively.