Renal vascular and tubular effects of vanadate in the anesthetized rat

The purpose of these experiments was to establish the renal vascular and tubular effects of vanadate. Three groups of adult rats were anesthetized with Na pentobarbital and given an i.v. infusion of a physiological saline solution at 0.055 ml/min. After a 60-min equilibration period, mean arterial blood pressure was measured, as were clearances of para-amino-hippuric acid (CPAH) and inulin (Cin), urine flow (V) and osmolality (Uosm) and the excretion rates of Na (UNaV), of K (UKV) and of Ca (UCaV). After the initial measurements, the i.v. infusion of physiological saline was continued in group 1 (controls), while vanadate was added to the saline and infused at 0.07 and 0.14 microM/min in groups 2 and 3. Then, all measurements were repeated. Compared with the control group, the following dose-dependent changes were observed in the vanadate-infused rats: increased mean arterial blood pressure, decreased CPAH (effective renal plasma flow), decreased Cin (glomerular filtration rate), increased V, UNaV and UCaV and decreased Uosm and UKV. Both the renal vascular and renal tubular effects of vanadate are similar to the renal effects of ouabain, previously reported by others. These effects can be explained by inhibitory effects of vanadate on Na,K-adenosine triphosphatase (ATPase) and/or Ca/ATPase activities of renal vascular and tubular cells.