Distribution, surface density, and membrane area of diadic junctional contacts between plasma membrane and terminal cisterns in mammalian ventricle

Abstract

The surface density of diadic junctional complexes (DJC) between plasmalemma and terminal cisternal membrane, as well as the areas of plasmalemmal and cisternal membrane involved in DJC, have been determined morphometrically in external plasmalemmal envelope and T-system of rabbit, rat, and mouse ventricular heart muscle. In all three species, both the surface density and the plasmalemmal area of DJC are 4- to 6-fold greater in the T-system than in the external plasmalemmal envelope. The surface density and DJC membrane area per unit cell volume and per unit myofibrillar volume increase in the order rabbit