Dietary vanadium and the oxidative state of hepatic and renal pyridine nucleotides

Effects of in vivo vanadate administration on calcium exchange and contractile force of rat ventricular myocardium

The aim of this study was to evaluate the effect of a 14-day intragastric administration of Na3VO4 (0.03 mmol/kg daily) on calcium metabolism and contractile force of rat myocardium. Left ventricular pressure as well as its first derivative (dP/dt) were registered with a balloon inserted to this ventricle and the cellular content of exchangeable calcium with the aid of 45Ca2+. Left ventricular pressure of the hearts exposed to vanadium was 11.8 +/- 0.2 kPa and was lower by 23% in comparison with control hearts (without vanadate), and its first derivative was 131.01 +/- 2.8 kPa/s (lower by 36.4%). The cellular content of exchangeable calcium in myocardium of rats treated with vanadium was 1.305 +/- 0.173 and 2.019 +/- 0.231 mmol/kg of wet weight (w.w.) in the stimulated and in the rested (for the last 10 min) ventricles, respectively. Accordingly, in the control group, the Ca content in stimulated hearts was lower by 0.384 mmol/kg w.w., and in the rested ones it was lower by 0.715. This indicates that the myocardial contractile force decreases, in spite of the fact that the content of calcium is considerably higher than that in the control group. These results also show a toxic effect of vanadate on the myocardium, probably due to large intracellular accumulation of calcium and cell damage.

Lipid peroxidation and antioxidant enzymes in vanadate-treated rats

Male Wistar rats received an aqueous solution of ammonium metavanadate (AMV) of 0.15 mg/V/ml concentration instead of water for 14 days. The erythrocyte count and haemoglobin level in blood were not changed; the haematocrit index was slightly increased. The spontaneous lipid peroxidation in kidney and liver homogenates was increased. The Fe(II)- or ascorbate-induced lipid peroxidation was more pronounced in the kidney than in the liver. No changes in lipid peroxidation were observed in erythrocytes after AMV treatment. The AMV treatment resulted in a decrease in the activity of the antioxidant enzymes, catalase and glutathione peroxidase in the kidney and liver; the cytosolic Cu,Zn-SOD and mitochondrial Mn-SOD were unchanged. The activity of the enzymes in blood was not changed. The results are discussed with a view to the participation of lipid peroxidation in vanadium toxicity.