Characteristics of cells dissociated from mouse mammary glands: I. Method of separation and morphology of parenchymal cells from lactating glands

Abstract

Mammary tissue from lactating mice can be dissociated by treatment with collagenase and separated into relatively pure adipose-cell and parenchymal-cell suspensions by centrifugation in hypertonic sucrose solution. DNA measurements indicate that the yield of parenchymal cells is about 20 % of total cells in the original tissue. The frequency of occurrence of distinctive light cells at all stages in the procedure suggests that lactating mammary cells are exceptionally vulnerable to mechanical and other traumata. Electron-microscope examination shows that incubation of tissue in non-nutrient medium with or without collagenase causes, in surviving cells, distortion of Golgi bodies and mitochondria and disappearance of microtubules and of specialized structures of the cell surface. The dissociation procedure further induces consistent vesiculation of the endoplasmic reticulum and, in cells fully detached from one another, loss of morphologic polarity. Many alveolar cells, however, remain interconnected by tight junctions and retain some polarity. Surviving cells readily recover from the osmotic effects of passage through hypertonic sucrose solution. Addition of glucose to the dissociation medium prevents the more extreme modifications of organelle and cell-surface structure. However, cells dissociated without glucose recover much of the cytoplasmic organization characteristic of their initial secretory state when incubated with glucose and an amino acid, leucine. These cell preparations compare favorably with tissue slices in their ability to convert glucose, acetate, and leucine to carbon dioxide and fatty acids, although synthesis of lactose and protein is somewhat lower than in slices given the same substrates.