Prostaglandin F-2 alpha causes regression of an hCG-induced corpus luteum before day 5 of its lifespan in cattle.
The experimental objective was to evaluate how a spontaneously formed corpus luteum (CL) differed in its response to prostaglandin (PG) F-2 alpha, given during the first 5 days after ovulation, from a CL induced during dioestrus with hCG. Sixteen Holstein heifers were used during each of 2 consecutive oestrous cycles. During the first cycle (sham cycle), heifers were given no PGF-2 alpha (control) or PGF-2 alpha (25 mg, i.m.) on Day 2, 4 or 6 (oestrus = Day 0). During the second cycle (hCG-treated cycle), heifers were given hCG (5000 i.u., i.m.) on Day 10, followed by no PGF-2 alpha (control) or PGF-2 alpha on Day 12, 14 or 16, corresponding to 2, 4 or 6 days after the ovulatory dose of hCG. A new ovulation was induced in 13 of 16 heifers given hCG on Day 10. Luteolysis did not occur immediately in heifers given PGF-2 alpha on Day 2 or 4 during the sham cycle, but concentration of progesterone in serum during the remainder of the cycle was lower in heifers given PGF-2 alpha on Day 4 than in sham controls or heifers given PGF-2 alpha on Day 2 (P less than 0.05). Luteolysis occurred immediately in heifers given PGF-2 alpha on Day 6 of the sham cycle or on Day 12, 14 or 16 of the hCG-treated cycle, with concentration of progesterone in serum decreasing to less than 1 ng/ml within 2 days.(ABSTRACT TRUNCATED AT 250 WORDS)
Howard
H J
HJ
Department of Animal Science, North Carolina State University, Raleigh 27695-7621.
Britt
J H
JH
D000818:Animals; D002417:Cattle; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D003338:Corpus Luteum / Q000187:drug effects*; D015237:Dinoprost / Q000494:pharmacology*; D004958:Estradiol / Q000097:blood; D004971:Estrus / Q000187:drug effects; D005260:Female; D003341:Luteolysis / Q000187:drug effects*; D011374:Progesterone / Q000097:blood; D013997:Time Factors
D006063:Chorionic Gonadotropin; D011374:Progesterone; D004958:Estradiol; D015237:Dinoprost