Effect of polychlorinated biphenyls and thiamin deficiency on liver metabolism in growing rats

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Abstract
Weanling rats were fed a thiamln‐deficlent diet containing 0, 10, or 500 ppm Aroclor 1254 (AR) ad libitum for 28 days. Control animals without and with AR at both levels received an oral thiamin supplement. Fasting blood glucose levels were determined at weekly intervals. The effects of AR, thiamin deficiency, and their interaction on liver cytosol and mitochondrial redox states and on cytoplasmic phosphorylation state as calculated from metabolite concentrations in freeze‐clamped livers were determined. Liver lipid and various parameters of lipid synthesis, transport, and storage were also studied. A R treatment and thiamin deficiency resulted in enlarged livers, increased liver lipid, increased lipid synthesis, decreased plasma free fatty acids, and decreased carcass lipids. AR treatment and thiamin deficiency increased the oxidized state of the mitrochondrial NAD∗/NADH couples and similarly Increased the cytoplasmic NADP∗/ NADPH couple associated with isocitrate dehydrogenase activity. These effects were more pronounced in AR‐treated rats than in thiamin‐deficient rats. The oxidation of the NADPH couple for fat synthesis could account for only a fraction of the NADPH utilized. It is suggested that the remainder was used by an induced drug metabolizing cytochrome enzyme system.