Electron Microscopic Studies on the Morphogenesis of Fibrinoid Degeneration in the Mesenteric Arteries of Hypertensive Rats

Abstract

The mesenteric arteries of hypertensive rats with the bilaterally constructed renal arteries were examined in thin sections by electron microscope to elucidate the nature and morphogenesis of fibrinoid degeneration of arterial walls. Fibrinoid substance in the intima of these arteries was seen as an aggregate of electron-dense rod-shaped or massive substances, which were not homogeneous, but showed a stripe-pattern, resulting from parallel arrangement of dense threadlike substances. These latter showed regular cross-striations with a period of about 230 A, corresponding with the periodic cross-striations of fibrin. As for the morphogenesis of fibrinoid degeneration, it is considered that a large amount of blood plasma protein, especially fibrinogen, would "insudate" into the subendothelial layer, first by increased pinocytosis, that is, through the canalicular system of the endo-thelial cells, and afterwards through the widely opened spaces between the adjacent endothelial cells. There they are polymerized and fused to form fibrinoid substance.