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 o f freeze-dried ultrathin cryosections. The intracellular compartmentat ion 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 expos ed to 1-10 mu M cadmium without carbon dioxide supply, the potassium/s odium 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 expose d to 1-10 mu M cadmium with carbon dioxide supply, changes of the elec trolyte composition were delayed to 1-2 days. An increase of intracell ular chloride preceded the inversion of the intracellular potassium/so dium 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 mu M c admium in the presence of 100 mu M zinc with carbon dioxide for 1 day. Changes in the intracellular electrolyte composition by adverse or to xic conditions were detected before any structural damage became visib le. Thus, energy dispersive electron probe X-ray microanalysis of cryo sections proved to be a sensitive probe of cell viability and cytotoxi city. (C) 1997 Academic Press.