Histochemical and chronological analysis of mouse submandibular gland parenchyma subjected to abrupt reperfusion.

We examined the effects of abrupt reperfusion on the mouse submandibular gland parenchyma and determined the degree of recovery from tissue damage. A main trophic artery supplying the gland was ligated with silk thread, and the ligature was then released after a variable period. The gland was removed at various times after reperfusion and then examined immunohistochemically and ultrastructurally. With reperfusion after 15 or 30 min of ligation, the tissue damage to the glands was slight or inapparent. With reperfusion after 1 or 3 h of ligation, collapse of the acini and the ducts was observed in parts of the lobules, but restoration of the parenchymal structures occurred, with the appearance of PCNA-positive cells, although there were differences in the level of restoration. After 6 h of ligation, most of the normal parenchymal cells had disappeared by the 5th and 7th days after reperfusion, and apoptosis and necrosis were present. These findings suggest that if interruption of the blood supply to the submandibular gland parenchyma is limited to within a few hours, then tissue repair after reperfusion is possible, although this will differ according to the level of damage, because the acini and the ducts reappear, probably with proliferation of parenchymal cells.