The effect of different diets or mineral oil on liver pathology and polybrominated biphenyl concentration in tissues

Groups of 10 adult (3.5 months) male Sherman strain rats were given 0 or a single dose of 500 mg polybrominated biphenyls (PBB) in corn oil/kg by stomach tube. Three weeks later, groups of 10 rats each that had received 500 mg/kg and groups of 10 rats each that had been given corn oil were started on a purified 20% fiber or 4% fiber diet. Ten rats each that had received 500 mg/kg or corn oil were continued on Purina Chow. An additional group of 10 rats given 500 mg/kg was also continued on Purina Chow but was given 2 ml mineral oil/kg three times a week. All rats were given the different diets or the mineral oil for 3 months. Chemical analysis of blood, liver, and adipose tissue by gas chromatography for PBBs showed no statistically significant difference in the PBB concentrations in blood and adipose tissue among the different groups. The PBB concentrations in the liver of rats fed Purina Chow were significantly lower than in the other groups if they were calculated on a wet weight basis. When PBB concentrations in liver were calculated on a lipid basis, the differences were not statistically significant. Total liver lipids showed statistically significant increases in rats given 500 mg/kg followed by 4 or 20% purified fiber diet or by Purina Chow and 2 ml of mineral oil/kg every other day. Microscopic examination of the livers showed essentially normal parenchyma in all rats that had not received PBBs. The rats given a single oral dose of 500 mg/kg which was followed by Purina Chow or Purina Chow and mineral oil showed some centrolobular vacuolated hepatocytes and enlarged hepatocytes around the central veins. The vacuolation was more pronounced in rats receiving Purina Chow and mineral oil also. Rats given 500 mg/kg followed by 4 or 20% purified fiber diet showed severe steatosis of the liver with megalo-hepatocytes, areas of cell necrosis and interstitial fibrosis. The interstitial fibrosis was more pronounced in rats given the 20% purified fiber diet. These results indicate a pronounced additive effect on PBB liver toxicity in rats by the 4 or 20% purified fiber diets which may be deficient in some nutrients or may prevent absorption of important nutrients.