Effects of cadmium on electrolyte ions in cultured rat hepatocytes studied by X-ray microanalysis of cryosections.

The distribution of elements in isolated and cultured rat hepatocytes was measured by energy dispersive electron probe X-ray microanalysis of freeze-dried ultrathin cryosections. The intracellular compartmentation of electrolyte ions, in particular the content of sodium, chloride, and potassium, was found to depend on culture conditions and on the amount of cadmium chloride added to the culture medium. In cells exposed to 1-10 microM cadmium without carbon dioxide supply, the potassium/sodium ratio decreased from control values of about 10 to values below 1 within 30 min. Changes of potassium and sodium content were followed by an increase in the intracellular chloride content. In cells exposed to 1-10 microM cadmium with carbon dioxide supply, changes of the electrolyte composition were delayed to 1-2 days. An increase of intracellular chloride preceded the inversion of the intracellular potassium/sodium ratio. High cadmium doses induced a cytoplasmic calcium increase and finally disintegration and decay of cell structure. Almost normal potassium and sodium contents were found in cells exposed to 10 microM cadmium in the presence of 100 microM zinc with carbon dioxide for 1 day. Changes in the intracellular electrolyte composition by adverse or toxic conditions were detected before any structural damage became visible. Thus, energy dispersive electron probe X-ray microanalysis of cryosections proved to be a sensitive probe of cell viability and cytotoxicity.