A morphologic study of the recovery of the rat submandibular gland after retrograde infusion. II. Lipid-soluble radiographic contrast medium.

Abstract

Lipid-soluble radiographic contrast medium was infused retrogradely through the main excretory duct of the rat submandibular gland until ductal and slight parenchymal filling or heavy parenchymal filling was achieved, as determined by the developing intraglandular pressure. The glandular tissue was fixed by vascular perfusion at different times following infusion, and examined by light and electron microscopy. Dilation of the intralobular ducts and scalloping of the luminal border were pronounced after both degrees of filling. Widening of the acinar lumina and intercellular canaliculi occurred early. Masses of fused secretory granules were commonly seen in the cytoplasm of the acinar cells and formation of vacuoles occurred frequently. In some acinar cells, densely packed granules filled the major part of the cytoplasm. Large lysosomes and autophagic vacuoles, frequently present in the various parenchymal cells, often contained apparent contrast medium. In addition, widening of the intercellular spaces between parenchymal cells was seen, particularly in the acini and intercalated ducts. An inflammatory cell-infiltrate, primarily comprised of polymorphonuclear leukocytes, was particularly prominent at 20 h and 30 h after infusion. The changes were generally more pronounced and persisted for a longer time in glands subject to heavy parenchymal filling. Large cyst-like spaces surrounded by inflammatory cells were seen in the lobules and in the interlobular connective tissue of these glands. At later times, areas containing apparent contrast medium surrounded by macrophages, were frequently observed in the connective-tissue stroma. Atrophy of the parenchymal cells was seen later, after heavy parenchymal filling, and a proliferation of the connective tissue had occurred. The changes were most probably caused by the elevated intraglandular pressure induced during infusion, and the subsequent cell damage and inflammatory reaction. A foreign body reaction, induced by the retained lipid-soluble contrast medium, was probably partly responsible for the morphological alterations observed, following infusion.