Aspects of Intracellular Transit of Serum and Lipid Phases of Milk

Intracellular sites of origin of constituents of milk and mechanisms by which milk constituents are compartmentalized and transported to the apical cell surface for release into alveolar lumina have been studied by microscopists, physiologists, and cell biochemists over the past 25 or more yr. Through the efforts of these many investigators much has been learned about formation, transport, and secretion of milk constituents. However, the pace at which knowledge about milk formation has accumulated has been modest, and we have much to learn about the processes leading to formation and cellular release of milk. In view of the signal importance of lactation to mammalian life, it is regretable that so much remains to be learned about the differentiated mammary epithelial cell.