The acute effects of oestradiol-17beta and synthetic LH-RH on plasma LH levels in freemartin heifers.
Injection of oestradiol was followed by a surge of plasma LH within 24 h in only 7 of 12 freemartins. Elevations of plasma LH were less than those reported for normal non-cyclic heifers, but some freemartins showed a delayed, or more prolonged, LH response. Responsiveness to oestradiol was not related to degree of chimaerism or plasma androstenedione level, and most of the animals responded similarly in two trials carried out 4 months apart, during which time plasma androstenedione levels had more than doubled. Freemartins which showed an LH surge after oestradiol treatment released greater amounts of LH after the injection of LH-RH than did non-responders.
D000818:Animals; D002417:Cattle; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005611:Freemartinism / Q000097:blood*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000097:blood* / Q000378:metabolism
D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007986:Luteinizing Hormone