Prevention of implantation by [d-trp6]-LH-RH IN the rat: Comparative study with the effects of large doses of hcg on pregnancy

A. Arimura, E. Pedroza, J. Vilchez-Martinez, A. V. Schally

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Effect of large doses of [D-Trp6]-LH-RH and HCG on implantation of fertilized ova was examined in the rat. Subcutaneous administration of 6ug[D-Trp6]-LH-RH per day from days 1 to 5 of pregnancy by an implanted minipump completely prevented the implantation of fertilized ova associated with a dramatic reduction of plasma progesterone on days 4 and 8, with a slight reduction of estradiol on day 4. There was no balooning of the uterus in the exploratory laparotomy on days 8 and 14. Administration of 1000 U of HCG daily from days 1 to 5 partially prevented implantation and completely terminated gestation. However, plasma progesterone and estradiol levels did not differ from those in the control animals. Ovaries in the [D-Trp6]-LH-RH treated rats appeared to be the same in size as those of the control pregnant rats, whereas the ovaries of the HCG-treated rats were hypertrophied. The results suggest that [D-Trp6]-LH-RH prevents nidation through a mechanism different from that for the adverse effect of excess HCG on pregnancy.

Original languageEnglish (US)
Pages (from-to)357-366
Number of pages10
JournalEndocrine Research
Issue number6
StatePublished - Jan 1 1977


ASJC Scopus subject areas

  • Endocrinology

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