TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) causes an increase in protein tyrosine kinase activities at an early stage of poisoning in vivo in rat hepatocyte membranes.

TCDD was found to cause a significant rise in protein tyrosine kinase levels at an early stage of poisoning in rat liver membrane preparations. The results of sephadex G-150 column chromatographic analysis on rat hepatocyte membranes indicate that there are at least three tyrosine kinases of which activities increase as a consequence of TCDD treatment in vivo. The TCDD-evoked rise in such protein tyrosine kinase activity precedes the down-regulation of the EGF (epidermal growth factor) receptor in the plasma membrane in vivo.