[Comparison of the effect of the epidermal growth factor (EGF) and its cyanogen bromide derivative on EGF receptor phosphorylation and uridine uptake in a cell culture].

In contrast to the intact EGF, a cyanogen bromide derivative of EGF (EGF-CNBr) does not induce an increase in uridine phosphorylation rate in 3T3 cells, the ability of the EGF-CNBr to stimulate autophosphorylation of the EGF-receptor in A-431 cells being reserved. EGF and EGF-CNBr were used in concentrations promoting their equivalent binding with EGF receptor in both the series of experiments, which was necessary because of a decreased affinity to binding EGF-CNBr. Thus, the EGF-induced receptor autophosphorylation was not enough for uridine kinase activation. The differences between EGF and EGF-CNBr cellular processing made it possible to discuss potential ways of uridine-kinase activity regulation during the early period of stimulation of quiescent cell cultures.