Distribution of connexin37, connexin40 and connexin43 in the aorta and coronary artery of several mammals

Intercellular communication between cells of the vessel wall is established by a combination of diffusion and convection of humoral and endothelial fa ctors in the extracellular fluid or by direct intercellular contacts presen t in the form of gap junctions composed of proteins called connexins. At le ast connexin (Cx)37, Cx40 and Cx33 are expressed in the vessel wall, but di sparate findings with regard to the cell specific localisation of connexins in the vasculature indicate that the distribution of connexins may be spec ies and vessel specific. Moreover, differences in expression exist between cells in culture and tissue sections. We performed an inventory immunohisto chemical study on the localisation of Cx37, Cx40 and Cx43 on tissue section s of the bovine, micropig and rat aorta and coronary system, which represen t morphologically and functionally different types of vessels in the arteri al system. We could observe Cx40 labelling most commonly, although with var ious intensities, between endothelial and smooth muscle cells of the specie s studied, with the exception of rat aortic smooth muscle cells. The distri bution of Cx43 is more differentiated and mostly confined to smooth muscle cells, although it can be detected scarcely between endothelial cells. Cx37 , when detectable, is predominantly expressed between endothelial cells in a heterogeneous pattern. We conclude that Cx40 is the constitutive vascular gap junction protein in situ and guarantees cell coupling between cells in the vessel wall. The differentiated distribution of both Cx37 and Cx43 sug gests they are involved in more dynamic processes.