Blockade of the Pre-ovulatory LH Surge in Hamsters by an Inhibitory Analog of LH-RH

Antonio de la Cruz, David H. Coy, Andrew V. Schally, Esther J. Coy, Käte G. de la Cruz, Akira Arimura

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Cycling hamsters were injected s.c. with 750 μg of D Phe2 D Leu6 LH RH, an inhibitory analog of LH RH at 3, 4, 5, and 6 PM on the day of proestrus. Serum LH levels were determined by radioimmunoassay in samples collected throughout the afternoon of proestrus. Treatment with D Phe2 D Leu6 LH RH led to 82.8% suppression of the physiological surge of LH as compared with the integrated LH levels of diluent treated animals. When ova were counted, treatment with D Phe2 D Leu6 LH RH was shown to produce 29.6% (P<0.05) inhibition of ovulation as compared with diluent treated animals. No rebound phenomenon in serum LH was observed in the evening of proestrus in animals treated with the analog. Incomplete inhibition of ovulation may be due to the possibility that the small LH surge was well in excess of that needed to produce ovulation or could be synergized with an incomplete FSH surge which was not measured in this study. The small peaks of LH still present in the analog treated animals may be explained by the intrinsic gonadotropin releasing activity of the analog and/or the schedule of treatment used.

Original languageEnglish (US)
Pages (from-to)576-579
Number of pages4
JournalProceedings of the Society for Experimental Biology and Medicine
Issue number2
StatePublished - Jun 1975
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)


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