The distribution and excretion of 2,4,5,2',5'-pentachlorobiphenyl in the rat.

Rats received single intravenous doses (0.6 or 6.0 mg/kg) of 2,4,5,2',5'-pentachlorobiphenyl-14C (5-CB). The distribution and ecretion of 5-CB-derived material were investigated at periods ranging from 10 min to 42 days after administration and found to be first-order rate processes in the dose range studied. Blood, liver, muscle, skin, and adipose tissues were found to be the most important tissues to the distribution of this compound. More than 90% of the total dose was removed from the blood within 10 min after administration. Most of the radioactivity was initially deposited in the liver and muscle, and then translocated to the skin and adipose tissue. The decay rate of radioactivity from each of the tissues could be described by the sum of two or more exponentials. Metabolism to more polar compounds appears to be a prerequisite to excretion, and most of the radioactivity was excreted in the bile and ultimately in the feces. Excretion in the urine accounted for less than 7% of the total dose and ceased at approximately 8 or 9 days after 5-CB-administration. Studies of the distribution and excretion of 5-CB-derived material over extended periods of time, 1-42 days, demonstrated the importance of the adipose tissue and skin as long-term storage sites, and demonstrated that the decay rate of 5-CB from the tissues paralleled the decreasing rate of excretion in the feces.