Repair in arterial tissue. A semiquantitative scanning-electron-microscopic and light-microscopic study on the effects of toxic doses of noradrenaline on the endothelium of the rabbit thoracic aorta.

The effects of various numbers of intravenous toxic doses of noradrenaline observed at various time intervals after the injections were studied by scanning electron microscopy (SEM) and surface light microscopy of silver-stained rabbit thoracic aorta and by transmission light microscopy. Hexagonal endothelium: a conspicuous change was observed by SEM and surface light microscopy, increased with the length of observation time, and to a certain degree with the number of noradrenaline injections; this change occurred coincidently with development of media necroses, intimal thickening, dilatation of the vessel and various gross changes. Silver-binding endothelial cells: a discrete lesion prevailed in experiments based on one injection of noradrenaline and seemed partly independent of time of observation. The nature of these cells and their role in the morphology of noradrenaline lesion remained obscure. Hexagonal endothelium and silver-binding endothelial cells may have a partial common pathogenetic mechanism, but a mutual relationship was improbable.