Synthesis of apoprotein B of very low density lipoprotein in embryonic-chick liver. Development of responsiveness of oestrogen.
The influence of exogenous oestrogen on the rate of synthesis of the apoprotein B of very-low-density lipoprotein by embryonic chick liver has been examined at various stages of development. Significant synthesis of apoprotein B was found in the absence of hormone treatment as early as day 6 of egg incubation. This basal level of apoprotein B synthesis varied from 2.5--6% of total protein synthesis. Embryos at day 10 or earlier treated with oestradiol exhibited no increase in the basal level of apoprotein B synthesis. Embryos at day 11 responded to oestradiol slightly and, from days 12 to 20, oestrogen treatment raised the relative rate of apoprotein B synthesis significantly above basal values: the maximal rate was about 16% of total protein synthesis. The anti-oestrogen tamoxifen citrate abolished the hormone-induced increase in apoprotein B synthesis and was not itself oestrogenic. The basal level of apoprotein B production was not sensitive to tamoxifen citrate, either in relatively early or in later stages of development. The basal level of apoprotein B synthesis, therefore, is oestrogen-independent and under developmental control distinct from the hormone-sensitive synthesis. The ontogeny of oestrogen-responsiveness of apoprotein B production appears to parallel the acquisition of the hepatic oestrogen-receptor system [Lazier (1978) Biochem. J. 174, 143--152].
D000818:Animals; D001053:Apolipoproteins / Q000096:biosynthesis*; D002642:Chick Embryo; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004958:Estradiol / Q000494:pharmacology*; D008079:Lipoproteins, VLDL / Q000096:biosynthesis*; D008099:Liver / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D009928:Organ Specificity; D013629:Tamoxifen / Q000494:pharmacology; D013997:Time Factors
D001053:Apolipoproteins; D008079:Lipoproteins, VLDL; D013629:Tamoxifen; D004958:Estradiol