2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) alters 32P-labeling of guinea pig (GP) pancreatic membranes (PMs)

Min after giving TCDD (ip), circulating insulin levels are decreased. Since PM phosphorylation has an important role in regulating insulin, TCDD influence here was assessed. Male GPs were given TCDD (1-3ug/kg, ip) in corn oil/acetone or vehicle, PMs were isolated and 32P-labeled using [γ-32P]ATP. Differences in labeling are apparent after 1 to 3 h and greater than pair-fed controls after 24 h. 32P incorporation showed saturation kinetics at 0 and 30 degrees, was abolished with EDTA, and was enhanced by 12-0-tetradecanoylphorbol-13-acetate (3 ug), insulin (.1uM), and Ca2+ (<10-7M) (SDS-PAGE and filtration assays). Other ligands (epidermal growth factor (EGF), Ca2+ (.1mM) ± calmodulin, cAMP) showed no differences. A low MW species (<5 kDa) was consistently increased with TCDD. Phosphoaminoacid analysis showed only marginal increases in P-Tyr, which was associated more with the low MW species. EGF membrane binding was not different while SRC oncogene protein binding was increased with TCDD. The data indicate that TCDD altered PM tyrosine kinases, C-K, and other ATP hydrolases, and disposition of PM proteins to phosphorylation and possibly proteolytic step(s)