A methylsulphonyl metabolite of a polychlorinated biphenyl can serve as a ligand for alpha 2mu-globulin in rat and major-urinary-protein in mice.

1. Kidneys from rats given an intraperitoneal dose of 4,4'-bis[( 3H]methylsulphonyl)-2,2',5,5'- tetrachlorobiphenyl[(CT3SO2)2TCB)] contained (CT3SO2)2TCB associated with a protein which has been isolated and characterized by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), immunoblot and immunodiffusion analysis to be alpha 2 mu-globulin (alpha 2 mu). 2. The same radioactive alpha 2 mu-globulin complex was isolated from urine of rats given an i.p. dose of (CT3SO2)2TCB. This complex represented 12.3% (0.27% dose) and 9.3% (0.06% dose) of the radioactivity excreted in 0-24 h and 24-48 h urine, respectively. 3. The radioactivity was extractable from alpha 2 mu and characterized by t.l.c. (co-chromatography in two solvent systems) to be (CT3SO2)2TCB. 4. A radioactive-protein complex was isolated from urine of mice given an i.p. dose of (CT3SO2)2 TCB. The radioactive-protein complex was characterized to be mouse major urinary protein (MUP) by SDS-PAGE, immunoblot and immunodiffusion analysis. This complex was not detected in mouse kidney. 5. Urinary excretion of radioactive-MUP complex represented 51.7% (2.3% dose) and 28% (1.3% dose) of the radioactivity excreted in 0-24 h and 24-48 h urine, respectively.