Subcellular distribution of gold in rat renal cortex cells: Limitations of electron microscopy and subcellular fractionation techniques

Electron microscopic and subcellular fractionation studies of renal cortex tissue from male Sprague-Dawley rats given gold sodium thiomalate (16 mg Au/kg) were undertaken to investigate the subcellular distribution of gold in kidney tissue. Although gold was present in the nuclear fractions prepared by differential centrifugation, electron microscopic examination indicated extensive contamination by aurosomes, which pellet in the nuclear fraction due to their greater density. No gold could be detected in the nuclei of intact tissue preparations by energy dispersive X-ray analysis (EDA). This observation does not preclude the possible presence of dispersed gold at levels below the 500 μm limit of detection for EDA. Nuclei from control animals, which were free of contamination by lysosomes, took up gold(I) from an incubation medium to the extent of 2.0 μg Au/mg of nuclear protein, independent of the gold concentration. When the nuclei were lysed, the gold was associated with the membrane fraction.