Prolonged Release of LH and FSH and Depletion of Pituitary Gonadotropin Content after Administration of [d-LEU 6,desGly-NH 2 10 ]-LH-RH Ethylamide 1

Abstract

Summary

LH and FSH releasing activities of [D-Leu⁶, desGly-NH₂ ¹⁰]-LH-RH ethylamide were examined using immature male rats. The gonadotropin release induced by various doses of [D-Leu⁶, desGly-NH₂ ¹⁰]-LH-RH ethylamide followed a different pattern than when LH-RH was given, reaching a peak at 2 hr after injections, serum LH and FSH being still elevated at 4 hr. In contrast the LH and FSH release induced by LH-RH reached a peak in 15 min and declined at 1 hr. This provides further evidence that this analog is indeed long-acting. The LH-RH analog had a potency 20-60 times greater for LH release and 10-30 times higher for FSH release than LH-RH. [D-Leu⁶, desGly-NH₂ ¹⁰]-LH-RH ethylamide also caused a significant depletion of the pituitary gonadotropin content.

The authors express their thanks to Mrs. J. Gau-thier and Mrs. D. Pierson for their technical help, and to Dr. G. Niswender, Dr. A. Ward and NIAMDD Rat Pituitary Program for the gift of the Material used for radioimmunoassays.