Effects of progestagen treatment on concentrations of prostaglandins and oxytocin in plasma from the posterior vena cava of post-partum beef cows.
The role of PGF-2 alpha in determining the lifespan of corpora lutea in the post-partum beef cow was investigated. In control cows (N = 5) induced to ovulate at Day 28 to 36 post partum by injection of 1000 i.u. hCG, corpora lutea had an average lifespan of only 8 days. In cows pretreated with 6 mg implants of a progestagen (norgestomet, N = 4) for 9 days, with implant removal 2 days before injection of hCG, luteal lifespan averaged 17.5 days. Concentrations of PGF-2 alpha in 9 hourly samples of plasma collected from the posterior vena cava via indwelling catheters were higher on Days 4 through 9 after injection of hCG (P less than 0.05) in the cows with short-lived corpora lutea. Greater release of PGF-2 alpha could therefore be a major factor in premature luteal regression. Concentrations of PGFM and oxytocin did not differ between cows with corpora lutea of short or normal lifespan. In a second experiment, concentrations of PGF-2 alpha in plasma from the posterior vena cava were examined during treatment with norgestomet (N = 8) or in contemporary controls (N = 7). In progestagen-treated cows, PGF-2 alpha was higher than in control cows (P less than 0.05), beginning on Day 3 of treatment and peaking on Day 5. It is concluded that the post-partum uterus increases secretion of PGF-2 alpha very early after first exposure to endogenous or exogenous progestagen.
Cooper
D A
DA
Division of Animal and Veterinary Sciences, West Virginia University, Morgantown 26506.
Carver
D A
DA
Villeneuve
P
P
Silvia
W J
WJ
Inskeep
E K
EK
D000818:Animals; D002417:Cattle; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D003338:Corpus Luteum / Q000187:drug effects; D015237:Dinoprost / Q000031:analogs & derivatives / Q000097:blood* / Q000378:metabolism; D005260:Female; D003341:Luteolysis / Q000502:physiology; D010121:Oxytocin / Q000097:blood*; D049590:Postpartum Period / Q000097:blood*; D011247:Pregnancy; D011282:Pregnenediones / Q000494:pharmacology*; D045167:Progesterone Congeners / Q000494:pharmacology*; D011863:Radioimmunoassay; D014599:Uterus / Q000378:metabolism; D014682:Vena Cava, Inferior
D006063:Chorionic Gonadotropin; D011282:Pregnenediones; D045167:Progesterone Congeners; C008228:15-keto-13,14-dihydroprostaglandin F2alpha; C100284:norgestomet; D010121:Oxytocin; D015237:Dinoprost