Regeneration of endothelium in rat aorta after local freezing. A scanning electron microscopic study.

Immediately after freezing the abdominal aorta of rats by applying a cold probe, the endothelium is desquamated or necrotic and platelets adhere to desquamated areas (at the earliest observable time) but not to necrotic endothelium or endothelium adjacent to the injury. Preferential adhesion of platelets to fenestrations of the internal elastic laimina appears to lead to their active migration into the media, where a large number may be present up to 8 days after injury. Platelets seems to be removed from the surface by the action of the advancing edge of the regenerating endothelium, moving at a maximum mean rate of 590 mu daily. An increase in area of individual cells appears to relate better than an increase in their number to the advance of the edge of the regenerating sheet.