Rapid recovery of estrogen-induced pituitary gonadotropin surges after luteectomy in rhesus monkeys.
In the presence of a functional corpus luteum, positive estrogen feedback on the surge modes of gonadotropin secretion is blocked in rhesus monkeys. We investigated the effects of luteectomy (Lx) on the time required for recovery of pituitary responsiveness (LH/FSH surges) to positive estrogen feedback. Estradiol-17 beta-3- benzoate (EB, 50 microgram/kg sc) was given: 1) 24th prior to, 2) the day of, or 3) 24 h after luteal ablation. Daily measurements of serum follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol-17 beta (e2) and progesterone (P) were made on each monkey for 5 days. Serum P fell to undetectable levels within 24 h after Lx, whereas E2 levels in circulation peaked within 24h after injection of EB. Among early follicular phase monkeys, this EB treatment results in typical midcycle type LH/FSH surges within 48h. Lx alone was not soon followed by significant changes in pituitary gonadotropin secretion. When circulating P levels were undetectable the pituitary responded fully to EB; that is, typical midcycle type FSH/LH surges occurred. When serum P was in the midst of declining after Lx, gonadotropin surges were present, but attenuated. However, when P levels remained elevated for more than 24 h after EB injection, the surge modes of FSH/LH secretion remained fully blocked. These results demonstrate that the suppressive influence of luteal secretions (principally progesterone) on positive estrogen feedback regulation of the surge modes of pituitary gonadotropin secretion is quite transient in these primates.
D000818:Animals; D003338:Corpus Luteum / Q000502:physiology*; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood*; D007986:Luteinizing Hormone / Q000097:blood*; D008253:Macaca mulatta; D010710:Phosphates / Q000097:blood
D010710:Phosphates; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone