Relative gold-binding capacity of metallothionein: studies in renal cytosols of gold-injected rats.

To determine the gold-binding capacity of metallothionein (MT) in cytosols of gold-injected rats, we examined the relationship between gold contents in cytosols and in MT fraction in rat kidneys. Each rat was injected intraperitoneally once with 0.9% NaCl or gold (5, 10 or 20 mg gold/kg b.w.). The gold contents in kidneys and in MT fraction increased following the injected amount of gold. The distribution profiles of the renal cytosols of gold-injected rats on a Sephadex G-75 column showed that the amount of the increased gold was attributable to the high molecular weight proteins (HP) and the MT fractions. There were close relationships between the gold contents in cytosol and in MT fractions, and between the gold contents in cytosol and in HP fractions. These results demonstrate that 14% of the increased gold in the renal cytosols of gold-injected rats was bound to MT and that 79% of the increased gold was bound to HP. Our results suggest that the role of metallothionein in gold accumulation in kidneys is different from that in zinc accumulation in kidneys.