A stereological study of the volume-weighted volume and of the relative volume of the nucleus of normal and preneoplastic hepatocytes in a trout model of hepatocarcinogenesis

Abstract

The fish liver has been the main subject of the biomonitoring and laboratory studies dealing with environmental carcinogenesis. The foci of cellular alterations are accepted pre-neoplastic hepatic lesions, and histopathology is the primary tool for their characterization. Despite its potential, using stereology to study quantitatively nuclear features of those lesions has not been evaluated. Herein, we estimated the volume density and the volume-weighted volume of the nucleus of normal and preneoplastic hepatocytes, using stereology and the brown trout (Salmo trutta f. fario) as model. In the hepatocarcinogenesis protocol the N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was used as initiator, and the 17-β estradiol (E2) as promoter. Three groups of 30 animals were considered: negative controls (non-exposed), initiator exposed and initiator plus promoter exposed. Estimates of both stereological parameters were significantly higher in preneoplastic hepatocytes, also showing an excellent discriminatory power when used to differentiate those hepatocytes from the normal ones. Besides, in the normal parenchyma the two parameters also differed among the three tested groups. The exposure to MNNG and/or to E2 leaded to modifications in the hepatocyte nuclei that could be unbiasedly quantified with two stereological parameters. We showed that quantitative nuclear morphology represents a valuable auxiliary tool in assessing hepatocarcinogenesis in fishes.