Regeneration of exo- and endocrine pancreas. Morphological studies of lesions induced by ethionine or excess methionine.

Changes that were interpreted to be of regenerative nature were studied in Chinese hamsters treated with ethionine or excess methionine. Numerous ductules and associated nodules of rather large cells were seen in the light microscope. Ultrastructurally, the endoplasmic reticulum of unaffected and damaged acinar cells showed a whorled appearance. Exocrine cells with no or few zymogen granules and low or moderate cytoplasmic electron density were found. There were other exocrine cells that exhibited prominent endoplasmic reticulum consisting of vacuoles, vesicles, and cisternae, the latter containing electron dense masses. Occasional mitoses were seen in acinar and ductule cells. The endocrine pancreas showed some new formation of cells, with the occurence of granulated cells in ductules. It is suggested that, in pancreas damaged by the administration of ethionine or excess methionine; there is regeneration of acinar parenchyma by mitotic cell division, by restitution of damaged cells, as well as by new formation of cells from ductules. In addition, there is some new formation of endocrine cells.