210Po binding to metallothioneins and ferritin in the liver of teleost marine fish

Abstract

The subcellular distribution of the naturally occurring radionuclide "' PO was investigated in the Liver of the Atlantic mackerel Scomber scombrus. The majority of the 2'0Po was found in the cytosol of the liver cells. Fractionation of the cytosol proteins by high performance size-exclusion and ion-exchange chromatography indicated that about 30% of 210Po was bound to ferritin and approximately 28% to metallothioneins. The affinity of 210Po for these proteins was confirmed by a similar binding of the artificial Z08Po isotope incubated in vitro with the cytosolic proteins. Two other proteins, likely selenium-and zinc-containing enzymes, may also bind smaller amounts of 210Po, about 8 % each. The extensive binding of 'lOPo to ferritin and metallothioneins is not accompanied by a similar strong binding of 21uPb, the radioactive grandparent of "OPo, which explains the generally very high 210Po:210Pb ratio observed in fish tissues and, in particular, fish liver