Intermediate filaments and ATPase activity in the vascular wall of vertebrates

The vascular wall of aorta and vena cava was examined for adenosine triphosphatase (ATPase) activity and cytoskeletal intermediate filaments (IF) in different representatives of vertebrates. Enzyme activity was studied by the modified method of Padykula and Herman. A streptavididin-biotin immunohistochemical method was applied to reveal desmin (D) and vimentin (V) IF. Endothelial cells of all vessels were V-positive and D-negative and exhibit high ATPase activity. Vascular smooth muscle cells (SMC) in lower vertebrates (pisces and amphibia) were also V-positive and D-negative, but showed low ATPase activity. SMC were D-positive and V-negative and possessed high enzyme activity in aves and mammals, similar to that of the endothelium. In cow vascular wall D-reactivity and high ATPase activity were mostly expressed in bundles of mosaically arranged thick SMC fibres of the outer aortic media as well as in the longitudinal fibres in the inferior vena cava. In higher vertebrates SMC of vasa vasorum were both V- and D-positive and showed high enzyme activity. The results demonstrate that D-immunoreactivity is mostly expressed in SMC of layers of high functional activity, which correlates with the intense ATPase reaction in these cells.