Purification and Characterization of Mammary Myoepithelial and Secretory Cells from the Lactating Rat*

Abstract

Myoepithelial and secretory cells from the mammary gland of the lactating rat have been isolated, purified, and characterized. Mammary tissue was dissociated with collagenase into basket-like networks of myoepithelial cells and single secretory cells. Because of their larger size, the myoepithelial cell networks could be separated from other mammary and blood cells by differential centrifugation. Isolated secretory cells were purified by isopycnic centrifugation in 25% bovine serum albumin. The purified myoepithelial and secretory cells were viable, as shown by the incorporation of 32P into distinct macromolecules that were separable by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both myoepithelial and secretory cells retained their characteristic morphology after isolation and purification, as shown by light, transmission, and scanning electron microscopies. The isolated myoepithelial cells were unique and, thus, distinguishable from other mammary cells in a number of respects; they 1) contracted in response to the addition of oxytocin, 2) bound [3H]oxytocin specifically, 3) accounted for the content of alkaline phosphatase and [Na+ + K+]ATPase in mammary tissue, and 4) reacted specifically with antiserum prepared against purified myoepithelial cells. The purified secretory cells were unique in possessing glucose-6-phosphate dehydrogenase activity. The different cell markers not only gave independent estimates of the purity of the cell fractions, but they also may be helpful in identifying mammary cells in stages of differentiation and neoplastic transformation.

Clonal characterization of mouse mammary luminal epithelial and myoepithelial cells separated by fluorescence-activated cell sorting

“…Flow-sorting is the only feasible method for virgin mouse mammary epithelial cell sorting, as density gradient centrifugation and other physical techniques [e.g., (29)] are applicable only to pregnant/ lactating tissue in which the luminal cell density is altered by lipid accumulation. The quantities of tissue reasonably available are too small for methods such as immunomagnetic sorting (3), and immunopanning does not solve the problem caused by the presence of potentially mixed luminal-myoepithelial pairs in cell suspensions.…”

Oxytocin as feeding inhibitor: Maintaining homeostasis in consummatory behavior

“…It is released after dilation of the cervix during labor; in lactating animals, it stimulates milk ejection (Crowley et al , 1992, Soloff et al , 1980). Food intake, body weight and adiposity increase during pregnancy and persist throughout lactation to provide for the metabolic demands of the fetus and sustain milk production.…”

Involvement of P 2 -purinergic receptors in intracellular Ca 2+ responses and the contraction of mammary myoepithelial cells

“…They were distinguishable from secretory epithelial cells that were larger and contained many fat droplets in the cytoplasm. The buoyant density of the myoepithelial cells was higher than that of the secretory epithelial cells [24,28], so they were washed and mounted on glass slides in aqueous mounting medium (PermaFluor), then viewed using a fluorescence microscope (Olympus BHS). were isolated by means of Percoll density gradient centrifugation.…”