Effect of progesterone on prostaglandin F2 alpha secretion and outcome of pregnancy during cloprostenol-induced abortion in mares.
OBJECTIVE
To determine the role of progesterone in the regulation of endogenous prostaglandin F2 alpha (PGF2 alpha) secretion during cloprostenol-induced abortion and to investigate use of progestins to prevent prostaglandin-associated abortion.


METHODS
16 pregnant mares.


METHODS
To induce abortion, cloprostenol (250 micrograms/d) was administered daily until fetal expulsion or for up to 5 days. In experiment 1, 8 mares, 98 to 153 days' pregnant, received progesterone (300 mg/d) at 24-hour intervals for 5 days, starting 18 hours after the first cloprostenol administration. In experiment 2, 8 mares, 93 to 115 days' pregnant, received altrenogest (44 mg/d) at 24-hour intervals, starting 12 hours after the first cloprostenol administration. Historic control mares, 82 to 102 days' pregnant, received cloprostenol (250 micrograms/d) daily until fetal expulsion.


RESULTS
In control mares, fetal expulsion occurred after 2 to 3 cloprostenol administrations and was associated with significant increases in PGF2 alpha secretion. Abortion did not occur in 5 of 8 progesterone-treated mares and 8 of 8 altrenogest-treated mares, and endogenous PGF2 alpha secretion was inhibited, compared with values in aborting mares.


CONCLUSIONS
Circulating progestogen concentrations may have a role in the outcome of pregnancy during prostaglandin-induced abortion. Altered prostaglandin secretion may be a reflection of a direct effect of progesterone or may be caused by the abortion process.


CONCLUSIONS
Progestogens might be useful for prevention of abortion in mares in which pregnancy is at risk owing to diseases that are associated with excess prostaglandin secretion.
Daels
P F
PF
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Besognet
B
B
Hansen
B
B
Mohammed
H
H
Odensvik
K
K
Kindahl
H
H
D000034:Abortion, Veterinary; D000818:Animals; D003008:Cloprostenol; D015237:Dinoprost / Q000096:biosynthesis* / Q000097:blood; D004967:Estrogens / Q000097:blood; D005260:Female; D006736:Horses; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000662:veterinary; D011374:Progesterone / Q000097:blood / Q000494:pharmacology*; D013997:Time Factors
D004967:Estrogens; D003008:Cloprostenol; D011374:Progesterone; D015237:Dinoprost