[Dependence of epidermal growth factor activation on its affinity and oligomerization]. / Zavisimost' aktivatsii retseptora épidermal'nogo faktora rosta ot ego affinnosti i oligomerizatsii.

Epidermal growth factor receptor (EGF-R) oligomerization has been followed on A-431 cells using covalent labeling by 125I-EGF and EGF-dependent autophosphorylation of receptor-kinase. High molecular weight complexes corresponding to monomeric, dimeric, and trimeric forms of EGF-R are detected. The process of oligomerization occurs effectively at 37 degrees C while at 4 degrees C no oligomer formation is detected. PMA or ATP treatment reduces the number of high-affinity EGF-binding sites but has no influence on dimer formation. Dimerisation of the EGF-R in the absence of the ligand has been established on formalin-fixed A-431 cells.

[The effect of epidermal growth factor on protein phosphorylation in normal and transformed hepatocytes]. / Vliianie épidermal'nogo faktora rosta na fosforilirovanie belkov v normal'nykh i transformirovannykh gepatotsitakh.

Qualitative differences in the content of tyrosine-phosphorylated proteins in normal and transformed hepatocytes have been found using the method of two-dimensional electrophoresis. Epidermal growth factor (EGF) has induced quantitative changes in the spectra of phosphotyrosine-containing proteins in normal cells and qualitative changes in the transformed ones. Results of immunoprecipitation with antibodies against phosphotyrosine permit revealing a protein with Mm 50 kDa which is subjected to EGF-dependent tyrosine-phosphorylation in normal hepatocytes. The intensity of protein phosphorylation is 10 times higher in the transformed cells but the dependence of this process on the EGF is not exhibited. The role of protein-tyrosine-kinases in the transmission of a mitogenic signal and in liver carcinogenesis is discussed.

[Changes in the contents of epidermal growth factor and EGF-like polypeptides in the liver tissue of rats in N-nitrosodiethylamine-induced hepatocarcinogenesis]. / Izmenenie soderzhaniia épidermal'nogo faktora rosta i podobnykh emu polipeptidov v tkani pecheni krys pri gepatokantserogeneze, indutsirovannom N-nitrozodiétilaminom.

It has been determined that concentration of EGF-like substances in the liver of rats with N-diethylnitrosamine-induced hepatocarcinogenesis increases and reaches its maximum in tumours (50-150 ng/mg protein). In the regenerating liver the amount of these peptides does not exceed 10 ng/mg protein. High pressure gel-filtration of appropriate extracts has revealed EGF-competing substances with m. w. about 20-30 kD in the liver carcinomas. The presented data confirm that registered EGF-like substances belong to TGF-alpha peptides.

[Change in the number of epidermal growth factor receptors of hepatocytes during liver regeneration in rats]. / Izmenenie kolichestva retseptorov épidermal'nogo faktora rosta gepatotsitov pri regeneratsii pecheni u krys.

The number of epidermal growth factor (EGF) receptors was determined for rat's hepatocytes under condition of their regeneratory proliferation, following a partial hepatectomy. In the normal hepatocytes two classes of EGF-receptors are distinguished, with high and low affinity, respectively. As early as 2 hours after the partial hepatectomy the total number of EGF-receptors sharply decreases, those with high affinity being not determined at all. The patterns of autophosphorylation of EGF-receptors with low affinity, examined in regenerating liver hepatocytes, remained the same as in the intact liver: their kinase activity was EGF-dependent, tyrosine residues of receptor molecules, with molecular mass equal to 150-170 kDa, underwent phosphorylation.