Renal Actions of Orthovanadate in the Dog

Abstract

The renal effects of orthovanadate (VO₄) were examined in anesthetized mongrel dogs. Orthovanadate was infused into one renal artery in concentrations ranging from 0.075 to 1.5 μmole/min. All major effects were observed only in the infused kidney. Renal vascular resistance (RVR) rose with increasing doses from normal (1.5 mm Hg/ml/min) to as high as 36. In general, the higher the dose the higher the RVR. Identical relationships between dose and response were observed for GFR and RBF which fell dramatically. There was also a fall in the excretion of water, sodium, and potassium. The intense vasoconstriction induced by VO₄ (0.5 μmole/min) was ameliorated by volume expansion (5% body weight with Ringer's saline), papaverine (0.5 mg/min), and acetylcholine (40 μg/min). Despite all these there were only modest increases in fractional sodium and potassium excretion. Systemic hemodynamic changes of VO₄ were a slight increase in mean arterial pressure (99 ± 8 to 107 ± 4 mm Hg), decreased heart rate (100 ± 5 to 82 ± 9 beats/min). It appears that VO₄ has a predominately vascular effect on the dog kidney with no discernible tubular effects under the conditions of these experiments. While the mechanism of the vasoconstriction are not clear they may be related to the effect of VO₄ on the ATPase system of vascular smooth muscle.