INFLUENCE OF SEVERAL EXTRACELLULAR-MATRIX COMPONENTS IN PRIMARY CULTURES OF BOVINE MAMMARY EPITHELIAL-CELLS

Mammary epithelial cells, obtained from lactating cows, were cultured onto inserts coated with several components of extracellular matrix. T he influence of these components upon the maintenance of differentiati on has been determinated. Every day, alpha S-1-casein secretion was me asured by radioimmunoassay (RIA) in apical and basal compartments. Reo rganization of functional tight junctions was evaluated by measurement of transepithelial electrical resistance (TER). On EHS matrix, cells underwent alveolar structures and never established TER. alpha S-1-cas ein secretion strongly fluctuated with the day of culture. When plated onto fibronectin, cells reorganized a typical pavement and establishe d TER. Nevertheless, TER and casein secretion highly fluctuated. On la minin-coated inserts, a few cells bound to the substratum, dedifferent iated, and proliferated to confluency within 9 days. TER progressively increased to a stable level after 15 days. Casein was not recovered a fter 6 days. Cells on type I collagen-coated inserts reorganized an ep ithelial pavement within 2 days and quickly established a stable TER. They secreted apically high levels of casein during 2 weeks. As cells maintained their biochemical differentiation, the culture on type I co llagen-coated inserts seems an efficient model for primary culture of bovine mammary epithelial cells and allows studies of polarized alpha S-1-casein secretion.