Submaxillary gland recovery from obstruction. I. Overall changes and electron microscopic alterations of granular duct cells

Abstract

Rat submaxillary glands were ligated for 31 days and then the ligatures were removed. Groups of animals were killed after 31 days of ligation and 7, 15, 30, 60, 120, and 180 days after the ligatures were removed. Overall gland recovery was studied by light microscopy in 1.5 μ sections, while the fine-structure details of recovery in the exocrine cells of the granular duct were studied by electron microscopy. There is a pronounced morphologic similarity of glands ligated for 31 days to immature glands of neonatal rats. However, evidence of parenchymal cell death or mitotic activity is extremely rare and therefore gland recovery is the result of cell recovery, not the result of de novo cell differentiation. Evidence of secretory activity appears in acinar cells before it does in granular ducts. Prior to 30 days after unligation granular duct cells contain no secretion granules, almost no RER, and very small Golgi areas. After 30 days, small dense granules appear in the apical cytoplasm, and there is a slight increase of RER. At 120 days, a small number of these cells appear mature, i.e., they are full of large secretion granules and contain well formed RER and Golgi patterns. By 180 days the gland appears essentially normal but there are still fewer mature granular duct cells than in the control.