Effect of estradiol and progesterone on the rate of incorporation of radiolabeled arachidonate into phospholipids and triglycerides of the rat uterus.
To obtain information on the effect of estradiol (E) and progesterone (P) on the overall rate of the acylation and deacylation reactions with [3H]arachidonate ([3H]AA) in the rat uterus, we investigated the effect of chronic treatment of ovariectomized rats with 2-200 micrograms/day E-dipropionate (EPP) and with 2 mg P alone or with the combination of these steroids on the extent and the time course of the in vitro incorporation of [3H]AA into various phospholipids (PLs) and the triacylglycerol fraction (TG). The results demonstrate that physiologic doses of E leads to a rapid equilibrium of the deacylation-acylation cycle only in the case of phosphatidylinositol (PI) whereas at high (200 micrograms/day) dose level it exerts the same effect on phosphatidylcholine (PC), phosphatidylethanolamine (PE) as well as on TG. P alone has no remarkable effects in the ovariectomized rat, but it decreases markedly the incorporation of [3H]AA into PI and TG in intact animals. Furthermore, P decreases the incorporation of [3H]AA into PI in the ovariectomized rat treated with 2 micrograms/day EPP as well as attenuating the enhanced labeling of PC, PE and PI caused by higher doses. Time-course studies provide evidence that all of these effects of progesterone can be accounted for by its ability to decrease the rate of deacylation and, therefore, to prolong the time needed to attain equilibrium in the rates of acylation and deacylation reactions of the various lipids with arachidonate. These data offer a novel outlook on the regulatory role of progesterone and estrogens in uterine function.
D000215:Acylation; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D002855:Chromatography, Thin Layer; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D007700:Kinetics; D010052:Ovariectomy; D010743:Phospholipids / Q000378:metabolism*; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014280:Triglycerides / Q000378:metabolism*; D014599:Uterus / Q000187:drug effects / Q000378:metabolism*
D001095:Arachidonic Acids; D010743:Phospholipids; D014280:Triglycerides; D016718:Arachidonic Acid; D011374:Progesterone; D004958:Estradiol