| Abstract: | Winter flounder (Pleuronectes americanus) from Boston Harbor, Massachusett, undergo a progressive series of hepatic changes involving hydropic vacuolation of epithelial cells, biliary hyperplasia, and hepatocellular and cholangiocellular neoplasia. Severely affected fish often exhibit grossly visible lesions. To examine cell proliferation associated with these conditions, evidence for DNA synthesis was sought. Boston winter flounder livers were screened endoscopically to select fish with and without grossly visible hepatic lesions, and then injected intraperitoneally with bromodeoxyuridine (BrdU) 3 h before euthanasia. Incorporation of this nucleotide analog was visualized immunohistochemically in formalin-fixed, paraffin-embedded tissues. Basal epithelia in the gill and intestine stained strongly, as did renal hemopoietic epithelia. In contrast, renal tubular epithelia and cardiomyocytes did not stain. Normal appearing hepatocytes stained occasionally, whilst more frequent staining was observed in vacuolated and neoplastic hepatic epithelia. We conclude (1) that the BrdU assay as described here has potentially widespread application to the study of cell proliferation in fish tissues; (2) that vacuolated cells may actively proliferate in winter flounder liver from Boston Harbor; and (3) vacuolated cells may be involved in the neoplastic transformation of hepatic epithelia. |
