An X‐ray microanalysis survey of the concentration of elements in the cytoplasm of different mammalian cell types

Electron probe energy dispersive X‐ray microanalysis was performed on freeze‐dried tissue sections. The dry weight concentration of elements (mmole/kg dry weight) was measured in the cytoplasm of several cell types from adult mice and rats. This comparative investigation showed: (1) That the energy dispersive X‐ray spectrum of element concentration from the cytoplasm of a specific cell type allows one to distinguish this specific cell type from other cell types with considerable accuracy. (2) That there is a relationship between the concentration of the various elements and the ultrastructural features of the cytoplasmic regions being analyzed. For example, areas rich in ribosomes are also rich in P, K and Mg. (3) These data support the idea that K is directly involved in the control of protein synthesis. The catalog of element concentrations in the cytoplasm of 13 cell types from both mice and rats should be of value to others who seek to answer various questions about these cell types.