Toxicological effects in rats chronically fed low dietary levels of fumonisin B-1

The toxicity of low dietary levels of fumonisin B-1 (FB1), i.e. 1, 10 and 2 5 mg FB,;kg diet, were monitored in rats over a period of 24 months. No eff ects on the body weight gain and feed intake profiles were noticed, while t he relative liver weight was significantly (P < 0.05) reduced in the FB1-tr eated rats. Mild toxic effects, including single cell necrosis (apoptosis). proliferation of bile duct epithelial cells (DEC), and early signs of fibr osis, bile duct hyperplasia and in one case, adenofibrosis, were noticed in the liver of the rats fed the highest (25 mg/FB1/kg diet) dietary level. A significant (P < 0.05) increase in the level of oxidative damage was also noticed in the liver of the rats of high dosage dietary group. The toxic ef fects were less severe in the 10 mg FB1/kg dietary group, whilst only a few ground glass foci were observed in the 1 mg FB1/kg dietary group. Hepatocy te nodules, staining positively for glutathione-S-transferase (placental fo rm, PGST), were observed macroscopically in the 25 mg FB1/kg treated group and to a lesser extent in the 10 mg FB1/kg treated rats. The most prominent toxic lesions by FB1 (10 and 25 mg FB1/kg dietary groups) in the kidneys w ere restricted to the tubular epithelium manifesting as granular cast, necr osis, apoptosis, calcification and the presence of regenerative foci in the proximal convoluted tubules. The existence of a cytotoxic/proliferative th reshold with respect to cancer induction by FB, in rat liver became apparen t, with a dietary level of < 10-mg FB1/ikg diet as a no effect threshold fo r the induction of hepatocyte nodules. (C) 2001 Elsevier Science Ireland Lt d. All rights reserved.