X-ray microanalysis of electrolyte content of normal, preneoplastic, and neoplastic mouse mammary tissue

Intracellular sodium, chlorine, and potassium concentrations (mmol/kg dry weight) were determined by electron probe X-ray microanalysis of individual epithelial cells in freeze-dried 2-micrometer sections of mouse mammary tissue which were cut at -30 degrees. A model system was utilized in order to compare elemental content of cells from normal pregnant mammary tissue and preneoplastic and neoplastic mammary tissues from female BALB/cCrlMed mice. Animals were killed by cervical dislocation, and tissue was rapidly frozen in liquid propane. Normal mammary glands were obtained from primiparous mice at 16 to 17 days of gestation. Tissue from the hyperplastic alveolar nodule line D1 was removed from donor mice 12 to 16 weeks after transplantation into the cleared mammary fat pad. All mammary adenocarcinomas, D1T, were primary tumors which developed in mice with transplants of nodule line D1. Data were collected from five animals (10 cells/animal) in each of the three groups. It was found that the electrolyte content of cells of preneoplastic tissue was the same as that of the normal mammary tissue but was significantly elevated in neoplastic tissue (162, 130, and 48% increases for sodium, chlorine, and potassium, respectively). Thus, an increase in electrolyte content seems to be associated with the transformation to a neoplastic state and not associated with conversion to the preneoplastic state.