Effect of RU 486 on luteal function in the early pregnant rat.
A dose of 30 mg RU 486/kg, an antiprogesterone, was administered to pregnant rats on Day 2 (Group 1) or Day 4 (Group 2) of pregnancy. RU 486 significantly changed serum progesterone and oestradiol concentrations and luteal 3 beta-HSD and 20 alpha-HSD activities in Group 1, and implantation was significantly inhibited. The luteal 3 beta-HSD activity in Group 2 rats on Day 6 was significantly (P less than 0.01) lower than the control value (7.5 +/- 0.6 and 10.1 +/- 0.6 mU/mg protein respectively). This decline in the 3 beta-HSD activity was followed by a marked decrease in the serum progesterone concentration, resulting in a significant decrease of the progesterone/oestradiol ratio and implantation was completely inhibited. The 20 alpha-HSD activity, which could not be detected on Day 6 in the control rats, was twice as great in Group 2 than in Group 1 rats (17.5 +/- 1.2 and 7.4 +/- 3.1 mU/mg protein respectively). Ultrastructural examination of corpora lutea of Group 2 rats confirmed luteolysis. These results suggest that RU 486 has a luteolytic effect and its anti-implantation effect is concomitant with luteolysis of the corpora lutea of pregnancy.
Kawano
T
T
Department of Obstetrics and Gynaecology, Kumamoto University Medical School, Japan.
Okamura
H
H
Tajima
C
C
Fukuma
K
K
Katabuchi
H
H
D015089:20-Hydroxysteroid Dehydrogenases / Q000378:metabolism; D015096:3-Hydroxysteroid Dehydrogenases / Q000378:metabolism; D000818:Animals; D003338:Corpus Luteum / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D010064:Embryo Implantation / Q000187:drug effects; D004958:Estradiol / Q000097:blood; D004963:Estrenes / Q000494:pharmacology*; D005260:Female; D015735:Mifepristone; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains
D004963:Estrenes; D015735:Mifepristone; D011374:Progesterone; D004958:Estradiol; D015096:3-Hydroxysteroid Dehydrogenases; D015089:20-Hydroxysteroid Dehydrogenases