Short-Term Distribution, Metabolism, and Excretion of 2,2′,5-Tri-, 2,2′,4,4′-Tetra-, and 3,3′,4,4′-Tetrachlorobiphenyls in Prepubertal Rats

Abstract.

The excretion and tissue retention of three ¹⁴C-labeled lower chlorinated biphenyls were examined in prepubertal male and female Sprague-Dawley rats following IV administration. Urine and feces were collected individually at different time intervals up to 72 h for pharmacokinetic analyses. After 72 h, different organs were removed and extracted in acetone:hexane (1:1, v/v) to determine radioactivity. Within the first 10 h after dosing, 2,2′,5-trichlorobiphenyl (PCB 18) was rapidly excreted in urine (8–18% of the administered dose), whereas only 0.6–0.8% of 2,2′,4,4′-tetrachlorobiphenyl (PCB 47) and 0.3–0.8% 3,3′,4,4′-tetrachlorobiphenyl (PCB 77) were found in urine during this time period. The half-life of elimination was shortest for PCB 18 (37.5 to 49.2 h). The half-lives for PCB 47 and PCB 77 were 351 to 672 h and 152 to 186 h, respectively. The cumulative total excretion (urinary + fecal) of PCB 18 within 72 h was 51–62%, of PCB 77 was 22–25%, and of PCB 47 was 7–10%. No parent PCBs were detected in urine. PCB 47 accumulated preferentially in adipose tissues (subcutaneous fat > mesenteric fat); relatively high levels of PCB 47 were also found in adrenals, ovaries, lungs, liver, and skin. The highest concentration of PCB 77 was found in serum, followed by adipose tissues. Very low concentrations of PCB 18 were found in most tissues; the highest being found in serum, followed by ovaries and adrenal glands. This study suggests that prepubertal rats retain higher short-term serum levels and have lower excretion rates than adult rats.