Centrally mediated effect of vanadate on diuresis and natriuresis in normal rats. Interaction with ouabain

Subchronic treatment with vanadate does not potentiate the toxicity of cardiac glycosides

Since it has been claimed that vanadate is an endogenous regulator of Na/K-ATPase activity and that it potentiates the toxicity of cardiac glycosides, we were alarmed to discover that certain Finnish physicians were prescribing vanadate in combination with other trace minerals to elderly patients for many different chronic diseases (e.g., cancer, rheumatism). To study the interaction of vanadate and cardiac glycosides, we fed vanadate in the drinking water (25 micrograms/mL) to guinea pigs for 20 d, and studied either their sensitivity to the acute toxicity of the cardiac glycoside ouabain or whether the vanadate would influence the subacute toxicity of ouabain. Vanadate had no influence on the toxicity of ouabain either acute or subchronically administered, nor was there any sign of inhibition of Na/K-ATPase activity as measured by 86Rb-uptake into intact erythrocytes (RBCs), RBC content of sodium or potassium or Na/K-ATPase activity in RBC membranes prepared from the vanadate-treated guinea pigs. Vanadate had been absorbed in substantial quantities from the gastrointestinal tract, since serum, heart, liver, and especially kidney contained measurable amounts of vanadium in contrast to controls, but it is concluded that this vanadate is not in a biologically active form.

Effect of agents which alter the Na transport on the sodium appetite in rats

The effect of ouabain (OUA), ethacrinic acid (EA) and diphenylhydantoin (DPH) on sodium appetite was evaluated in sodium-depleted rats. These animals were injected with either OUA (50 pg) or EA (150 ng) into the third ventricle (3V), fourth ventricle (4V), lateral ventricle (LV), or lateral hypothalamus (LH). Decreased Na appetite was observed only after injections either into the 3V or LV. DPH injection (270 ng) enhanced sodium appetite in mildly depleted rats. These effects seem to be specific for Na appetite since EA and OUA injections into the 3V did not alter food intake in food-deprived rats. The drugs did not impair gustatory inputs since the water-glucose preference was not altered after OUA, EA or DPH administration. The decrease in Na appetite induced by a 3-hour infusion of OUA (1 microliter/hr) was reversed by a 3-hour infusion of DPH (1 microliter/hr), while a pretreatment with DPH prevented the inhibitory effect of OUA. The data show that agents which inhibit cellular Na efflux such as OUA and EA decreased sodium appetite while DPH, which inhibits cellular Na influx, induced the opposite effect, i.e., enhanced Na appetite. The results are consistent with the hypothesis that the Na content of sensor cells located on or near the walls of the 3V could be the signal for the central control of Na appetite.