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.