REGULATION OF VASOMOTION OF ARTERIOLES AND CAPILLARIES IN THE CAT SPINAL-CORD - ROLE OF A ACTIN AND ENDOTHELIN-1

Ring-shaped vasoconstrictions of arterioles at their branching sites h ave often been reported in vascular corrosion casts of the brain and s pinal cord in rats and cats. It is surmised that smooth muscle cells i n arteriolar walls could regulate the blood flow by changing the diame ter of the lumen (ie vasomotion). However, few reports have described vasomotion at the capillary (capillaries have no smooth muscle cells). Also, there have been no reports on endothelin-l in the arterioles an d capillaries of the spinal cord. This study was designed to determine (1) the electron microscopic architecture of vasomotion; (2) the immu nohistochemical identification of alpha actin and endothelin-l in the arterioles and capillaries of the spinal cord. Twenty-seven adult mong rel cats were used to study vascular corrosion casts at the lumbosacra l spinal cord segments immunohistologically and through scanning elect ron microscopic observations. Sections of the spinal cord were stained with monoclonal anti-alpha actin and endothelin-l antibodies. Vascula r corrosion casts demonstrated two types of vasomotion: a sausage-like peristalsis and a ring-shaped vasoconstriction at the arteriole and c apillary levels. In the immunohistological study, alpha actin and endo thelin-l were identifiable in the vascular wall at the bifurcation, an d pericytes were found to contain microfilaments of alpha actin. The r ing-shaped vasoconstriction might be regulated by smooth muscle cells in arterioles and by pericytes in capillaries by releasing endothelin- 1.