Effect of trilostane on PGE, PGF₂α, estradiol-17β, and progesterone secretion and pregnancy of 90-day ovariectomized pregnant ewes

Ninety-day pregnant sheep were ovariectomized and received vehicle or trilostane every 12 h through 132 h, starting at 72 h postovariectomy. All trilostane-treated ewes aborted (P ≤ 0.05) between 36 and 50 h after initiation of treatment. Profiles of progesterone in jugular venous blood differed (P ≤ 0.05) and was lower (P ≤ 0.05) in trilostane-treated ewes. Profiles of estradiol-17β in jugular venous plasma of trilostane-treated ewes differed (P ≤ 0.05) from controls. Estradiol-17β increased after the first two treatments, followed by a return 2 h later to pretreatment levels (P ≥ 0.05), which was followed by a sustained increase (P ≤ 0.05) in estradiol-17β. Profiles of PGF₂α in inferior vena cava plasma of trilostane-treated ewes differed and were greater (P ≤ 0.05) and occurred with the sustained increase in estradiol-17β and the onset of most of the abortions. Profiles of PGE in inferior vena cava plasma between control and trilostane-treated 90-day pregnant ewes did not differ (P ≥ 0.05). It is concluded that abortions occur at midpregnancy in sheep when the estradiol- 17β : progesterone ratio changes sufficiently to cause a sustained increase in estradiol-17β and PGF₂α but without changing placental secretion of PGE.