Uncoupling of an Epithelial Cell Membrane Junction by Calcium-Ion Removal

Abstract

Calcium takes part in maintaining ion communication between salivary gland cells (Chironomus thummi). Its withdrawal from the cell systems results in virtual disconnection of ion communication, at Ca⁺⁺ concentrations which do not noticeably affect cell adhesion. The junctional membrane surfaces. which are normally quite freely permeable to ions, become as impermeable as the nonjunctional membrane surfaces; each cell seals itself off irreversibly as a unit. In maintaining ion communication Mg⁺⁺ substitutes for Ca⁺⁺