Characterization of a binding protein for the PCB metabolite 4,4'-bis(methylsulfonyl)-2,2',5,5'-tetrachlorobiphenyl present in bronchoalveolar lavage from healthy smokers and non-smokers.

Bronchoalveolar lavage (BAL) was performed in a group of healthy subjects (10 smokers and 10 non-smokers) and the recovered fluid was shown to contain specific binding sites for a metabolite of a polychlorinated biphenyl (PCB), 4,4'-bis ([3H]methylsulfonyl)-2,2',5,5'-tetrachlorobiphenyl [(3H-MeSO2)2TCB]. The sites seem to reside within a protein-like component and the apparent dissociation constant (Kd) for the binding was approximately 2 X 10(-7) M regardless of the smoking status of the subject. However, the maximum number of binding sites (Bmax) was significantly lower for the smokers (p less than 0.001). Competition studies indicated that some PCB methyl sulfones had similar affinities for the specific binding sites as (MeSO2)2TCB. Physicochemical characterization of the human (3H-MeSO2)2TCB-binding protein indicated a Stokes radius of 22 A and a sedimentation coefficient of 1.9 S, and on the basis of these parameters an apparent molecular weight of 17,700 was calculated. The binding protein had an apparent pI of 4.9. It is suggested that the specific binding protein for certain PCB methyl sulfones in bronchoalveolar lavage fluid from healthy subjects is responsible for the previously observed tendency of PCB metabolites to accumulate in human lung tissue.