Effect of actinomycin D on uterine prostaglandin production and oestrous cycle length in guinea-pigs.
Intrauterine, but not systemic, administration of actinomycin D on Day 10 increased oestrous cycle length in guinea-pigs. Peripheral plasma progesterone levels remained elevated during these lengthened cycles presumably because luteal life-span had been extended. Prostaglandin (PG) F-2 alpha production in vitro, on Day 15, by the uterus of guinea-pigs which had received intrauterine actinomycin D was much lower than control values. This decrease in PG production was not due to lack of precursor, increased metabolism, re-direction of synthesis towards PGE-2, or a direct inhibition by actinomycin D of the conversion of arachidonic acid to PGs. The effects of actinomycin D treatment were not reversed by oestradiol. It is proposed that actinomycin D prevents the increase in uterine PG synthetase levels that normally takes place after Day 11, thereby reducing uterine PGF-2 alpha synthesis and output in vivo, and resulting in luteal maintenance and longer oestrous cycles.
D000818:Animals; D003609:Dactinomycin / Q000494:pharmacology*; D004971:Estrus / Q000187:drug effects*; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D011458:Prostaglandins E / Q000096:biosynthesis*; D011460:Prostaglandins F / Q000096:biosynthesis*; D011863:Radioimmunoassay; D014599:Uterus / Q000187:drug effects / Q000378:metabolism*
D011458:Prostaglandins E; D011460:Prostaglandins F; D003609:Dactinomycin; D011374:Progesterone