Plasma Progestins, Estradiol, and Luteinizing Hormone Following Prostaglandin F2α Injection

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Abstract
Dairy cows, ranging from days 8-13 of the estrous cycle, were fitted with indwelling jugular catheters 1 day prior to either i.m. injection of prostaglandin F2 .alpha. [PGF2 .alpha.; 30 mg, n = 4] or intrauterine deposition of PGF2 .alpha. free acid (10 mg, n = 3). Blood samples were collected at 6, 4, 2 and 0 h prior to administration of PGF2 .alpha. and at 1, 3 and every 2 h thereafter until ovulation. Progestins, estradiol and luteinizing hormone in plasma were measured by radioimmunoassay. Hormonal changes and interrelationships within animals were evaluated by least squares analyses. Decreases in progestins of plasma within 24 h indicated PGF2 .alpha. induced luteolysis in 6 of the 7 animals. Estradiol increased linearly from time of injection to 52 h postinjection. Intervals from administration of prostaglandin to onset of estrus, peak of luteinizing hormone and ovulation were 74.9 .+-. 21, 78.8 .+-. 21 and 99.5 .+-. 19 h.
Funding Information
  • National Institutes of Health