ALTERATIONS IN PROTEIN-SYNTHESIS IN RAT-LIVER CELLS BY INVITRO AND INVIVO EXPOSURE TO 2,3,7,8-TETRACHLORODIBENZO-PARA-DIOXIN

Alterations in protein synthesis in rat liver cells were examined following in vitro and in vivo exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Primary cultured rat liver parenchymal cells were exposed to 1 nM TCDD for 23 and 47 hr. Synthesis of two proteins with molecular weights (M(r)) of 26,000 and 39,000 (designated 26k-P and 39k-P, respectively), other than cytochrome P450, was increased markedly in the cells. These proteins did not have the same antigens as cytochromes P450IA1 and P450IA2. Synthesis of three proteins with M(r)s of 24,000 25,000 and 29,000, respectively, was decreased by TCDD. TCDD was administered to rats at a dose of 100-mu-g/kg body weight. The amount of five proteins (two proteins with M(r) of 26,000, one of 36,000 and two of 39,000) was increased in TCDD-treated rat liver. However, the proteins increased in vivo by TCDD were distinguishable from 26k-P and 39k-P by two dimensional gel electrophoresis.