title: Blood LH after PGF2alpha in diestrous and ovariectomized cattle.
abstract: Two experiments were conducted to determine whether the increased serum LH which occurs within 12 hr after a luteolytic dose of PGF2alpha is dependent upon changes in progesterone or estradiol secretion. In the first experiment, exogenous progesterone abolished the increase in serum LH caused by a subcutaneous injection of 25 mg PGF2alpha in diestrous heifers, but not in ovariectomized  heifers. In the second experiment, progesterone pessaries were removed at 6 hr after a subcutaneous injection of 25 mg PGF2alpha. LH remained at pre-PGF2alpha values while the pessaries were in place, but began to increase within 1 hr after they were removed. Blood estradiol also remained at pre-PGF2alpha values until the pessaries were removed, and began to increase at 2 hr after pessary removal. We conclude that the increase in serum LH within 12 hr after PGF2alpha treatment in diestrous cattle is dependent upon withdrawal of progesterone; it is not due to increased serum estradiol.
mesh_terms: D000818:Animals; D002417:Cattle; D003338:Corpus Luteum / Q000502:physiology*; D004031:Diestrus / Q000187:drug effects*; D004958:Estradiol / Q000097:blood; D004971:Estrus / Q000187:drug effects*; D005260:Female; D007986:Luteinizing Hormone / Q000097:blood*; D010053:Ovary / Q000502:physiology; D011247:Pregnancy; D011374:Progesterone / Q000097:blood / Q000494:pharmacology; D011460:Prostaglandins F / Q000494:pharmacology*
chemical_list: D011460:Prostaglandins F; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone