Characterization of gold in the cytosol of rat-kidney cortex cells

Evidence is presented for a chemical equilibrium of gold(I) among sulfhydryl binding sites in the cytoplasm of renal cortical cells of the rat. The gold distribution among protein and nonprotein species, examined by gel-permeation chromatography following in vivo administration of gold sodium thiomalate, gold sodium thioglucose, NaAuCl₄, and (C₂H₅)₃PAuCl, was similar in each case, although the cytoplasmic gold concentrations varied. The pattern of gold elution closely parallels that of the thiol groups in the supernatant. In vitro addition of gold sodium thiomalate to the supernatant fraction produced an identical distribution. Addition of cysteine to cytoplasm following in vivo administration of gold drastically decreased the protein-bound gold and increased the non-protein-bound gold. These data rule out the induced synthesis of a metallothionein-like gold-binding protein. Ultracentrifugation revealed gold to be present in the microsomal fraction as well as the supernatant.