Repair in arterial tissue

Summary

The effects of severe toxic doses noradrenaline were evaluated by surface light microscopy and SEM of silver-stained thoracic aortae from young male albino rabbits.

Noradrenaline 1 mg a day was given i.v. for 14 days; the rabbits were killed on the 17th day. Rabbits injected by physiologic saline served as controls. Noradrenaline induced excessive blood pressure elevation, exitement and pulmonary edema, and at autopsy ascites, hydrothorax, dilatation of the aortae with plaques and calcifications was prominent. The thoracic aortae, silver-stained and fixed in situ, were studied by surface light microscopy and by SEM. Besides normal endothelium the following changes were observed alone or in combination: hexagonal patterns of silverlines, change of individual endothelial cells, and various miscellaneous changes. The hexagonal endothelium was considered genuine endothelium adapted to a mechanical dilatation of the aorta, but it also might reflect reparative processes and the effects of hemodynamic forces on endothelial morphology. The changed endothelial cells seemed by light microscopy to be permeable to silver, which stained the cell body and left the nuclear zone free. By SEM these cells were intensively silver-stained, folded and shrunken with nuclear swelling, and they looked severely damaged. A direct toxic effect of noradrenaline on endothelial cells was suggested, however, the damaging effect probably was composite. A causal relation between changed endothelium and hexagonal endothelium i.e. the hexagonal endothelium compensates loss of damaged cells by proliferation or by expansion, presupposes a fast expulsion of damaged cells, and remains open to question. The chronology of the changes induced by noradrenaline so far remains unknown.