Function of abnormal corpora lutea in vivo after GnRH-induced ovulation in the anoestrous ewe.
Anoestrous Romney Marsh ewes with and without progesterone treatment (+P, -P) were treated with small-dose (250 ng) multiple injections of GnRH at 2-h intervals for 48 h. Animals were slaughtered on Days 4, 5, 7 and 11 after the end of GnRH treatment and luteal function was assessed by the measurement of daily plasma progesterone concentrations. In all animals which ovulated (29/32, 91%) peripheral progesterone concentrations rose to 0.5-1.0 ng/ml within 3 days of the end of GnRH treatment. In 7/7 (100%) +P animals and 5/22 (23%) -P animals, progesterone concentrations continued to rise and were maintained at levels greater than 1.5 ng/ml until slaughter. In the remaining -P animals, plasma progesterone concentrations declined to reach basal levels by Day 5. Corpora lutea recovered from these animals showed signs of premature regression on Day 5 and were fully regressed by Day 7. Progesterone priming delayed the occurrence of the LH surge which occurred 39.1 +/- 3.6 h after the end of GnRH treatment in the +P animals compared to 20.2 +/- 1.74 h (P less than 0.001) in the -P animals in which luteal function was abnormal and 22.4 +/- 4.35 h in the -P animals in which luteal function was normal. These results show that abnormal luteal function occurs in the majority of GnRH-treated ewes in the absence of progesterone pretreatment.(ABSTRACT TRUNCATED AT 250 WORDS)
D000780:Anestrus / Q000502:physiology*; D000818:Animals; D003338:Corpus Luteum / Q000187:drug effects*; D004971:Estrus / Q000502:physiology*; D005260:Female; D007986:Luteinizing Hormone / Q000378:metabolism; D003341:Luteolysis; D010062:Ovulation Induction; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology*; D011374:Progesterone / Q000097:blood / Q000494:pharmacology; D012756:Sheep
D010906:Pituitary Hormone-Releasing Hormones; D011374:Progesterone; D007986:Luteinizing Hormone