Acute Effects of Vanadate Oligomers on Heart, Kidney, and Liver Histology in the Lusitanian Toadfish (Halobatrachus didactylus)

The contribution of vanadate oligomers to the acute histological effects of vanadium was analyzed in the heart, kidney, and liver of Halobatrachus didactylus (Schneider, 1801). A sublethal vanadium dose (5 mM, 1 mL/kg) in the form of metavanadate (containing ortho and metameric species) or in the form of decavanadate (containing only decameric species) was intraperitoneally administered by injection, and specimens of H. didactylus were sacrificed at one and seven days postinjection. Sections of heart ventricle and renal and hepatic tissue were stained with hematoxylin-eosin and examined by light microscopy to identify vanadium-induced tissue injury. In addition, PicroSirius-stained ventricular sections were analyzed by bipolarized light microscopy to determine the fraction of myocardium occupied by the ventricular wall structural elements (collagen I, collagen III, and cardiac muscle). Both vanadate solutions produced similar effects in the renal tissue. Morphological alterations included damaged renal tubules showing disorganized epithelial cells in different states of necrosis. Reabsorbed renal tubules and hyperchromatic interstitial tissue were also observed. The hepatic tissue presented hyperchromatic and hypertrophied nuclei, along with necrotic and hypertrophied hepatocytes, and more severe changes were observed in the liver with exposure to decavanadate. Vanadate oligomers promoted evident tissue lesions in the kidney and liver, but not in the cardiac tissue. However, cardiac tissue structural changes were produced. For example, decavanadate induced a hypertrophy of the ventricle due to a decrease in the percentage of myocardium occupied by collagen fibers. In general, decavanadate was shown to be more toxic than metavanadate.