Oxytocin Receptors and Mammary Myoepithelial Cells

Abstract

Oxytocin causes milk ejection by the mammary gland by eliciting contraction of myoepithelial cells, which surround the epithelial cells of the alveoli and the finer ducts (18). Most of the work reported here has been done with lactating rats. In this species expulsion of milk is almost entirely dependent upon the action of oxytocin (5, 15, 16). Effects of oxytocin upon mammary myoepithelial and uterine smooth muscle cells are mediated by oxytocin receptors, which have been characterized (for review see 37). These specific receptor sites have been defined by specificity of tissue and ligand and by correspondance between the dose of oxytocin giving a half-maximal response and die apparent Kd for oxytocin binding. With exceptions of changes in the affinity of binding sites for oxytocin, increases in specific oxytocin binding are equated to increases in oxytocin receptor concentration. This report reviews studies showing that oxytocin receptors in the mammary gland are specifically associated with isolated myoepithelial cells. © 1982, American Dairy Science Association. All rights reserved.