Ethionine induced degeneration and regeneration in the rat parotid gland: an electron microscope study.

The object of the present study was to establish a model for the study of parotid gland regeneration. Adult female Spague-Dalley rats were placed for 11 days on a protein-free diet with daily intraperitoneal doses of aqueous DL-ethionine equivalent to 0.5 hg/gm body weight, and returned to a normal diet on day 12. At varying intervals, both during and after intoxication, animals were sacrificed and the parotid glands prepared for study with the transmission electron microscope. Ultrastructural observations indicated that damage was essentially limited to the acinar cells, in which the protein synthetic apparatus was the focus of injury. The rough endoplasmic reticulum displayed atypical configurations, loss of attached ribosomes and membrane fragmentation. In the Golgi region, an atypical structure, a "crystalloid" arose during intoxication. Because of the morphology and apparent formation of the "crystalloid," it was assumed to be an abnormal secretion product. Resumption of a normal diet resulted in the rapid restitution of the normal cytoarchitecture. During the first week of recovery, there was prominent mitotic activity in mature acinar cells. It was concluded that the primary effect of ethionine upon the parotid gland is interference with the function of the protein-synthetic apparatus, leading to morphologic alteration of the acinar cells. The mitotic activity observed during recovery indicated that in the adult rat, acinar cells retain the potential for proliferation.