4,4′-Dichlorobiphenyl: Distribution, metabolism, and excretion in the dog and the monkey

The tissue distribution, metabolism, and excretion of 4,4′-dichlorobiphenyl (4,4′-DCB) were investigated in beagle dogs and cynomolgus monkeys ( Macaca fascicularis). Following a single iv dose of [ 14C]4,4′-DCB (0.6 mg/kg) excreta, blood, and tissues were collected at time intervals ranging from 15 min to 28 days for determination of levels of parent compound and its metabolites. Elimination of the parent PCB in the blood of both species was biphasic with a terminal-phase elimination rate constant of 0.018 hr −1 for the dog and 0.002 hr −1 for the monkey. By 24 hr the dog excreted 50% of the dose in the feces (43%) and the urine (7%). The percentage dose remaining was found largely as parent compound in the fat with some in muscle and skin. By 5 days 90% of the dose was excreted. In contrast, during the first 24 hr the monkey excreted less than 15% of the dose with less than 1% in the feces. The percentage dose remaining in the body was localized as parent compound in fat (33%) with lesser amounts in skin and muscle. By 28 days 59% of the dose was excreted, primarily in the urine. In anesthetized dogs 33% of the dose was excreted into the bile within 2 hr, while the monkey excreted only 0.4% of the dose by that route. The data present a clear species variation between the dog and the monkey in both the rate and route of excretion of 4,4′-DCB.