The binding of gold to cytosolic proteins of the rat liver and kidney tissues: Metallothioneins

Male Wistar rats were given a single s.c. injection of 2.5 mg gold per kg body wt and the binding of gold to the cytosolic proteins was investigated over a period of 21 days. In both the organs. gold was bound to two groups of high and one group of low molecular weight cytosolic proteins. Gold was present in the metallothionein fractions (the low mol. wt Au-binding proteins) within 0.5 hr after exposure to gold. The binding of gold to the cytosolic proteins in the kidney was significantly higher. up to 17 times that in the liver. The incorporation of gold into the metallothionein fraction was complete within 24 hr in the liver but continued to increase over a period of four days in the kidneys. Up to 51 per cent of the cytosolic gold in the kidney was bound to the metallothionein fractions. It is suggested that the ‘metallothioneins’ may play an important role in the sequestration and the intracellular localization of gold, particularly in the kidneys.