ABSTRACT: The subcellular distribution of the naturally occurring radionuclide ²¹⁰Po was investigated in the liver of the Atlantic mackerel Scomber scombrus. The majority of the ²¹⁰Po 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 ²⁰⁸Po 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 ²¹⁰Po to ferritin and metallothioneins is not accompanied by a similar strong binding of ²¹⁰Pb, the radioactive grandparent of ²¹⁰Po, which explains the generally very high ²¹⁰Po:²¹⁰Pb ratio observed in fish tissues and, in particular, fish liver.

KEY WORDS: Polonium · Fish · Metallothionein · Ferritin

Published in MEPS Vol. 177 (1999) on February 11
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1999