Inhibition by estradiol of binding and mitogenic effect of epidermal growth factor in primary cultures of Xenopus hepatocytes.
We demonstrate here the presence of two classes of EGF (epidermal growth factor) binding sites in primary cultures of male Xenopus liver parenchymal cells. One of these corresponds to the high-affinity receptor described in other tissues and species, and which exhibits the property of autophosphorylation. The number of EGF receptors decreased sharply in freshly prepared cultures but recovered to maximum levels within 24 h thereafter. Addition of EGF and insulin to the hepatocyte cultures enhanced the rate of DNA synthesis as measured by the incorporation of [3H]thymidine. Estrogen abolished this increase, reducing the incorporation to that seen with hydroxyurea. At the same time, the addition of estradiol reduced the number or activity of EGF receptors in a dose-dependent manner. The latter paralleled the activation of transcription of vitellogenin genes in Xenopus hepatocytes so that a high rate of DNA synthesis is unnecessary for or incompatible with the activation of the steroid hormone-induced vitellogenin genes.
Wolffe
A P
AP
Bersimbaev
R I
RI
Tata
J R
JR
D000818:Animals; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004815:Epidermal Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D066246:ErbB Receptors; D004958:Estradiol / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism; D014982:Xenopus laevis
D007328:Insulin; D011956:Receptors, Cell Surface; D004958:Estradiol; D004815:Epidermal Growth Factor; D004247:DNA; D011494:Protein Kinases; D066246:ErbB Receptors