Lactogenesis induced by ovariectomy in pregnant rats and its regulation by oestrogen and progesterone.
Ovariectomy on day 19 of pregnancy augmented galactosyl transferase activity 24 h after surgery preceding by 6 h the significant alpha-lactalbumin accumulation. Progesterone, injected immediately after ovariectomy showed a clear inhibitory effect on both galactosyl transferase and alpha-lactalbumin concentration, measured 30 h after ovariectomy. However, once the synthesis of lactose has been induced, progesterone is no longer inhibitory. Oestrogen induced a significant increase in lactose synthetase activity but no effect was obtained on galactosyl transferase activity. Progesterone, in a time and dose dependent relationship, was capable of preventing the effect of estrogen on lactogenesis. The lactogenic action of oestrogen in ovariectomized pregnant rats might be due to a direct effect at the mammary gland level facilitating the action of prolactin or through an indirect effect mediated via an increase on prolactin release.
D000818:Animals; D002369:Castration; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D005700:Galactosyltransferases / Q000378:metabolism; D007768:Lactalbumin / Q000378:metabolism; D007785:Lactose / Q000096:biosynthesis*; D007788:Lactose Synthase / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000201:enzymology; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D004967:Estrogens; D011374:Progesterone; D007768:Lactalbumin; D005700:Galactosyltransferases; D007788:Lactose Synthase; D007785:Lactose