The effect of polychlorinated biphenyls on liver gluconeogenic enzyme activities in rats during exposure to cold

Rats were fed diets containing either 0, 75, or 400 ppm Aroclor 1254. after 2 weeks on the diets, 4 animals per group were placed in the cold at 4° for an additional 2 weeks. Rats maintained at 4° gained less weight and had decreased adipose tissue weights as compared with animals at 25°. Ingestion of Aroclor 1254, a polychlorinated biphenyl (PCB), increased liver weights in the cold and at ambient temperature. Blood glucose was also significantly decreased in the cold-exposed rats fed 400 ppm PCB. At both temperatures, PCB decreased the specific activity (μmoles/g liver/min) of phosphoenol-pyruvate carboxykinase (PEPck) and fructose-1,6-diphosphatase (FDPase). Cold exposure significantly incresed the activity of PEPck and glucose-6-phosphatase (G-6-Pase) in rats fed PCB. When the activities were expressed as total μmoles/100 g body weight/min to correct for PCB-induced hepatomegaly, no significant differences were observed in the key gluconeogenic enzymes for PCB-fed rats at 25°. At 4°, FDPase and G-6-Pase activities were significantly increased with PCB feeding. Malic enzyme was significantly increased with PCB at both temperatures, regardless of the method of calculation. PCB ingestion had no effect on mitochondrial pyruvate metabolism. These studies indicate that ingestion of PCB (as Aroclor 1254) does not alter the response of the gluconeogenic enzymes to cold exposure.