The effects of acute administration of cadmium chloride on renal hemodynamics in rats

The decreases of glomerular filtration rate (GFR) and renal blood flow (RBF) after acute administration of cadmium have been reported. The recent studies about renal failure induced by heavy metals revealed that the decrease of glomerular ultrafiltration coefficient is an important contributing factor in the onset of acute renal failure and that the changes of renal hemodynamics are less prominent factors. To clarify whether the changes of renal hemodynamics contribute to the decrease of GFR caused by cadmium, we evaluated the changes of renal hemodynamics and inulin clearance after acute intravenous infusion of cadmium chloride in rats. Cadmium chloride was continuously infused at the rate of 3.0 μmol/kg/min into SD rats. Mean arterial pressure was significantly increased immediately after the infusion of cadmium and unchanged during the experiment. 20 minutes after the infusion of cadmium, inulin clearance was decreaed by 70% of the control value but RBF and renal vascular resistance (RVR) were unchanged. Filtration fraction was significantly decreased. 30 minutes after the infusion of cadmium, inulin clearance was further decreased by 51% of the control value. At the period, significant decrease of RBF (72% of control value) and increase of RVR (156% of control value) were observed. Urinary excretion of sodium and the ratio of urinary sodium to urinary inulin excretion were unchanged until 20 minute and were significantly decreased 30 minuts after the infusion of cadmium. Urinary volume was not changed throughout the experiment. These data indicate that the initial decrease of GFR after the infusion of cadmium is resulted from the decrease of filtration fraction but not RBF, suggesting the contribution of tubuloglomerular feed-back system and that the changes of renal hemodynamics contributes to the following further decrease of GFR.