Effect of [D-Phe2, Pro3, D-Phe6] -Luteinizing Hormone Releasing Hormone, an Antagonist, on Preovulatory Gonadotropin Secretion in the Rhesus Monkey

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Abstract
Experiments were undertaken to ascertain the effects of [D-Phe2, Pro3, D-Phe6]-LHRH [luteinizing hormone-releasing hormone, luliberin], a LHRH antagonist, on endocrine events during spontaneous menstrual cycles in the rhesus monkey. The antagonistic activity of this peptide during the periovulatory portion of the menstrual cycle was demonstrated to varying degrees in the treated monkeys by 1 or more of the following observations: an immediate cessation of the LH [lutropin] and FSH [follitropin] surges, prolonged and/or discontinuous gonadotropin surges, LH and FSH peaks of diminished magnitude, the absence of concomitant LH and FSH midcycle peaks, suppression of serum estradiol concentrations and a failure to identify corpora lutea during laparoscopic visualization of the ovaries. Apparently an antagonist of LHRH can modify periovulatory endocrine events in primates; however, [D-Phe2, Pro3, D-Phe6]-LHRH was not sufficiently active at the dose employed to inhibit completely or uniformly gonadotropin surges and prevent luteinization.