Adult (5 months) male Sherman strain rats received a single dose of either 0 or 500 mg
polybrominated biphenyls (PBB) in
corn oil/kg
body weight by stomach tube. After an 18-month recovery period, serum and liver samples were examined. The primary serum
lipid response was an increase in
cholesterol (both free and esterified) and in total
phospholipids. The percentage of esterified
cholesterol was not significantly different from that of the controls, and no significant differences in the
cholesterol ester fatty acid composition were observed. Serum
triglycerides were also unaffected. In the PBB-dosed animals, the total hepatic
fatty acids contained significantly less
palmitic acid and more
stearic acid, consistent with an increase in
palmitic acid chain elongation activity. No significant differences could be detected in the n-3 or n-6
acids except for a slight decline in the content of 22:6 (n-3). Hepatic microsomal
phospholipids were slightly higher (per milligram
protein) in the PBB-dosed animals, and the
cholesterol content was lower. Consequently, the
cholesterol-
phospholipid ratio was reduced, and microsomes from the latter group appeared to have an altered
lipid domain on the basis of steady-state fluorescence anisotrophy measurements. In addition, total hepatic
thiobarbituric acid-reactive substances (assayed as
malondialdehyde) were significantly increased in the PBB-dosed animals. This observation appeared to reflect an increased susceptibility to peroxidative stress in the latter group, probably resulting from reduced membrane
antioxidant concentrations. The PBB-dosed rats had significantly lower serum
retinol levels and a reduced content of this
vitamin in liver microsomes. Microsomes were also deficient in
alpha-tocopherol in the PBB-dosed animals, although serum levels were normal.