Scanning Electron Microscopy of Normal and Vasospastic Monkey Cerebrovascular Smooth Muscle Cells

: Normal cytoarchitecture of smooth muscle cells of monkey cerebral arteries was studied using scanning electron microscopy after removal of adventitial connective tissue by hydrolysis with HCl. Cerebral arteries were also examined after contraction in vitro with prostaglandin F2 alpha (PGF2 alpha). Anterior cerebral arteries were studied after exposure for 6 days in vivo to whole blood, oxyhemoglobin, methemoglobin, bilirubin, mock cerebrospinal fluid, or supernatant fluid from an incubated mixture of autologous blood and mock cerebrospinal fluid. Normal smooth muscle cells were spindle-shaped and oriented circumferentially around the vessel. They were often grouped into bundles of 5 to 10 cells; bundles were recognizable because cells within them were joined by multiple intercellular contacts. Groups of smooth muscle cells oriented longitudinally were present outside the circular layers of cells. The adventitial surface of muscle cells was smooth apart from fine longitudinal striations in some areas. Arteries contracted with PGF2 alpha had markedly convoluted and folded cell membranes. Muscle cells of vasospastic arteries and of arteries exposed to oxyhemoglobin and supernatant fluid appeared identical to cells contracted with PGF2 alpha. The outer surface of cells of arteries exposed to bilirubin, methemoglobin, and mock cerebrospinal fluid were normal. Marked similarity between vasospastic smooth muscle cells and smooth muscle cells from arteries contracted with PGF2 alpha suggest that smooth muscle contraction occurs during "vasospasm" due to whole blood and to intrathecal injection of oxyhemoglobin.