Expression of Cx43 in Cardiac and Aortic Muscle Cells of Hypertensive Rats

Abstract

Gap junctions are seen at sites where the plasma membranes of two adjacent cells become closely apposed [1,2], reducing the intercellular space, which is usually about 200 nm wide, to a narrow gap of 2 nm (figures 1 and 2). In these regions, the two interacting membranes feature specialized microdomains characterized by the concentration of uniformely large protein assemblies named connexons (figures 1 and 2). These structures provide the wall of intercellular channels, that allow for the passage of ions as well as for the exchange from one cell to another of metabolites and second messengers up to lkDa [3,4]. Such a direct cell-to-cell exchange of molecules can be visualized using exogenous tracers, such as Lucifer Yellow [5]. After microinjection into individual cells, the intercellular diffusion of this tracer, which cannot cross the cell membrane, can be directly observed under a fluorescence microscope (figure 2). Gap junction channels are formed by the hexameric assembly of membrane-spanning proteins (figures 1 and 2), known as connexins, which in mammals belong to a family of 13 members [2]. Five of these proteins, referred to as Cx43, Cx45, Cx46, Cx40 and Cx37 have been identified in the cardiovascular system [6,7]. As yet, little is known about their physiological role and their possible changes in cardiovascular diseases.