Studies on the ontogenesis and the regulatory mechanisms of placental lactogen and insulin binding sites (receptor) in rat liver.
The ontogenesis of specific binding of 125I-hPL and 125I-insulin was determined in rat liver cell membranes (10(5) X g pellets), and the regulatory mechanisms of these binding sites were also examined. There were striking differences in the mode of ontogenesis between binding sites of hPL and insulin in rats. HPL binding sites were very few in liver cell membranes from fetal and immature rats. They began to increase after puberty, and markedly increased in late pregnancy. On the other hand, insulin binding sites, which decreased in late pregnancy, were dominant in fetal liver and placenta. Consequently, the lipolytic and glycogenolytic activities of hPL in maternal liver were accentuated, whereas the effects of insulin on maternal liver were suppressed. In contrast, in fetal liver and placenta only the anabolic effects of insulin seemed conspicuous. According to the results of experiments on in vivo administration of estradiol-17 beta, progesterone, hydrocortisone or hPL to intact or hypox-rats, and the measurement of serum rat chorionic mammotropin (rCM), rPRL, estradiol-17 beta, and insulin during pregnancy in rats, the increase in hepatic hPL binding sites observed in late pregnancy might be, at least in part, due to rCM secreted from placenta, and the decrease in insulin binding sites due to the increase in serum insulin itself in rats.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D004958:Estradiol / Q000097:blood; D005260:Female; D006854:Hydrocortisone / Q000494:pharmacology; D007016:Hypophysectomy; D007328:Insulin / Q000097:blood; D007700:Kinetics; D008099:Liver / Q000196:embryology*; D049590:Postpartum Period; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology; D011388:Prolactin / Q000097:blood; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D011972:Receptor, Insulin / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018000:Receptors, Peptide
D007328:Insulin; D011956:Receptors, Cell Surface; D018000:Receptors, Peptide; C028202:placental lactogen receptor; D011374:Progesterone; D004958:Estradiol; D011388:Prolactin; D011972:Receptor, Insulin; D006854:Hydrocortisone