X-ray microanalysis of HeLa S3 Cells. I. Instrumental calibration and analysis of randomly growing cultures.

Cryo-ultramicrotomy and X-ray microanalysis were used to study the elemental composition of HeLa S3 cells. Quantitation was achieved by reference to elemental standards of known concentration made up in 25% gelatin. Analysis of standards showed linear calibration for each of the elements studied: Na, P, S, Cl, K. Standardization was validated by comparing flame-photometric analysis of gelatin containing sodium potassium tartrate with that of X-ray microanalysis. Freeze-dried sections of cells showed good morphology and analysis of whole sections of the cells showed that K/Na varied in individual cells. Low K/Na could not be ascribed to cell damage or to the sequestering of Na in any particular subcompartment of the cells. Treatment with ouabain caused changes in levels of all the elements studied and resulted in a low K/Na ratio in all cells.