Cytological study of vacuolated cells and other aberrant hepatocytes in winter flounder from Boston Harbor

A light and electron microscopic study of hepatocytes in winter flounder (Pseudopleuronectes americanus) from Boston Harbor has revealed 3 types of abnormal parenchymal cells in the livers of these fish. (a) Electron-lucent or "light" appearing hepatocytes had the following cytological features indicative of necrosis and cell death: an overall edematous (hydropic) appearance; swollen nuclei with marginated chromatin; moderately swollen, dense mitochondria with flocculent densities; fragmented profiles of endoplasmic reticulum membranes; and lysosome-like bodies. (b) Electron-dense or "dark"-appearing hepatocytes were shrunken and irregular in shape, had a highly condensed cytoplasm, and had dense nuclei that frequently contained vacuoles. In addition, variably sized, organelle-containing fragments of these cells were infrequently observed in adjacent "light" hepatocytes or histiocytes possibly resulting from apoptosis. (c) Vacuolated hepatocytes arranged in ductular or acinar configurations demonstrated signs of chronic cell injury such as numerous autophagic vacuoles, condensed mitochondria, and a modified endoplasmic reticulum system, the dilated cisternae of which appeared to form the large vacuole of the cell. While experimental verification is lacking, it is presumed that the various hepatocyte alterations observed in these fish were induced by environmental hepatotoxins.