The presence of two (Na+ + K+)-ATPase inhibitors in equine muscle ATP: vanadate nad a dithioerythritol-dependent inhibitor

The elements of life and medicines

Which elements are essential for human life? Here we make an element-by-element journey through the periodic table and attempt to assess whether elements are essential or not, and if they are, whether there is a relevant code for them in the human genome. There are many difficulties such as the human biochemistry of several so-called essential elements is not well understood, and it is not clear how we should classify elements that are involved in the destruction of invading microorganisms, or elements which are essential for microorganisms with which we live in symbiosis. In general, genes do not code for the elements themselves, but for specific chemical species, i.e. for the element, its oxidation state, type and number of coordinated ligands, and the coordination geometry. Today, the biological periodic table is in a position somewhat similar to Mendeleev's chemical periodic table of 1869: there are gaps and we need to do more research to fill them. The periodic table also offers potential for novel therapeutic and diagnostic agents, based on not only essential elements, but also non-essential elements, and on radionuclides. Although the potential for inorganic chemistry in medicine was realized more than 2000 years ago, this area of research is still in its infancy. Future advances in the design of inorganic drugs require more knowledge of their mechanism of action, including target sites and metabolism. Temporal speciation of elements in their biological environments at the atomic level is a major challenge, for which new methods are urgently needed.

Vanadium pentoxide phytotoxicity: effects of species selection and nutrient concentration

Vanadium concentrations in soil can be increased through anthropogenic inputs and can be harmful to plants. A Petri dish experiment was conducted to assess the effect of vanadium toxicity on the germination and survival of the garden lettuce, Lactuca sativa. A second study was conducted in a greenhouse to investigate the influence of species selection and nutrient concentration on the toxicity of vanadium pentoxide to plants. L. sativa and four non-crop native plant species, two grasses (Elymus virginicus and Panicum virgatum) and two broad-leaved species (Lycopus americanus and Prunella vulgaris) were selected. Artificial soil was used in both experiments, and a geometric progression of five vanadium concentrations plus controls was selected for the soil treatments. Results of the Petri dish experiment showed that seedling survival is a less sensitive end point than above-ground dry weight (DW) as measured in the greenhouse experiment. Nutrient level (100, 10, and 1 kg/ha) was found to strongly influence vanadium toxicity in the greenhouse study. At 100 kg/ha, plant tolerance to vanadium was greatest, as indicated by higher no-observed, lowest-observed, and percentage effect concentration values. Results showed that forbs (L. americanus and P. vulgaris) tended to be more sensitive than both the crop (L. sativa) and grasses (E. virginicus and P. virgatum) at high concentrations of vanadium. Soil concentrations resulting in a 25 % decrease in shoot DW were generally less than the Canadian soil quality guideline for vanadium, suggesting that 130 mg/kg may not be protective of the Canadian native plant species used in this study.

Computerized modeling of adenosine triphosphate, adenosine triarsenate and adenosine trivanadate

Computerized molecular models of adenosine triphosphate, adenosine tri-arsenate and adenosine trivanadate have been generated using the molecular mechanics technique. The analysis of structural parameters indicated that, at least theoretically, adenosine triarsenate is a realistic candidate for replacement of adenosine triphosphate in biochemical pathways. On the contrary, the structural arrangement of the inorganic segment of adenosine trivanadate does not seem to be capable of withstanding a swift hydrolytical splitting in aqueous milieu. It was shown that the universal force field as implemented in Gaussian software packages is an appropriate tool for the optimization of less-common bioactive compositions.

Vanadate stimulates tyrosine phosphorylation of two proteins in Raji human lymphoblastoid cell membranes

A membrane fraction from Raji human lymphoblastoid cells exhibited tyrosine-specific kinase activity. Vanadate increased tyrosine phosphorylation up to 5-fold; serine and threonine phosphorylation were unchanged. The stimulation was detectable within 15 s at 0 degrees C and at concentrations of vanadate (0.3 and 1.0 microM) present in normal tissues and blood. The tyrosine phosphorylation of two substrates, M1 61 000 and 55 000, was dependent upon vanadate and incorporation into these substrates represented the majority of the vanadate-sensitive tyrosine phosphorylation.

Effect of vanadate on reproductive efficiency in normal and streptozocin-treated diabetic rats

The effects of oral vanadate treatment on the reproductive efficiency of normal and diabetic female rats were studied. Vanadate treatment in a dose-dependent manner reduced both the conception rate and the ability to carry pregnancy to term compared with a control group. These effects were more severe in diabetic groups as compared with nondiabetic groups. At the 0.25 mg/mL vanadate dose, the conception rate was reduced by 13% and 33% for the nondiabetic group and the diabetic group, respectively. At the 0.50 mg/mL dose, this rate decreased by 20% and 47% for the nondiabetic and diabetic groups, respectively. With an identical oral vanadate regimen of 0.25 mg/mL, the ability to sustain pregnancy to term was reduced by 30% and 90% for the nondiabetic and diabetic groups, respectively, and by 84% and 100% for these groups at a dose of 0.50 mg/mL. Although the blood vanadate concentrations were an order of magnitude higher in diabetic animals treated with vanadate than in nondiabetic animals under an identical vanadate treatment, oral vanadate treatments had no measurable effects in ameliorating hyperglycemia in these diabetic pregnant animals. In conclusion, vanadate is ineffective in normalizing blood glucose in pregnant diabetic rats, and it impairs reproductive capacity and the ability to sustain pregnancy to term in both nondiabetic and diabetic animals.

Inhibition of insulin receptors by vanadate and ouabain

Insulin binding studies were performed, using cells from 5 non-obese, non-diabetic subjects, on four separate days: 2 were paired control studies to demonstrate precision, and 2 other sets were binding studies in which one incubation solution was a control and the other contained either vanadate, (10(-4) M) or ouabain (10(-4) M). For both substances tracer binding of 125I insulin was reduced significantly, 27% by vanadate and 30% by ouabain. Furthermore, at all points on the binding curve these substances inhibited binding by 18-98%, in a pattern consistent with reduced receptor number. The concentrations of vanadate or ouabain which we used did not change cell volume or inhibit trypan blue dye exclusion, as an index of cell viability. Because vanadate and ouabain inhibit Na+K+ATPase and have largely dissimilar effects on a variety of cell systems, our observations may reflect specific involvement of Na+K+ATPase in binding or closely related processes.

The effect of vanadate on Na+,K+-ATPase activity of mouse cerebral cortex during bicuculline-induced seizures

The effect of bicuculline-induced seizures on Na+,K+-ATPase activity of mouse cerebral cortex homogenates, using two different procedures of sample preparation (freezing in situ or decapitation of animals without freezing) is described. Regardless of tissue treatment Na+,K+-ATPase activities during bicuculline-induced seizures did not differ significantly from the appropriate controls when vanadate-free ATP was used as substrate. The response of Na+,K+-ATPase to K+ activation was also similar; the increase in potassium concentration from 2 to 20 mM caused a 33.0 and 32.3% increase of enzyme activity in cortical homogenates from control and convulsing mice, respectively. Vanadate added to the assay medium inhibited Na+,K+-ATPase activity in a dose-dependent manner; with both types of tissue treatment there was, however, a tendency towards lesser inhibition of the enzyme from convulsing mice and at 1 X 10(-7) M vanadate this difference, though slight, was statistically significant: -22.59 vs -27.55% (freezing) and -28.73 vs -38.42% (decapitation) for seizures vs controls, respectively. The reduced sensitivity of Na+,K+-ATPase towards vanadate inhibition in cortical homogenates prepared from mice with convulsions suggests that vanadate might play a role in the modulation of enzyme activity during seizures in vivo.

Alkaline phosphatase activity and tetracycline incorporation during initial orthodontic tooth movement in rats

The activity of alkaline phosphatase and the incorporation of tetracycline as signs of bone formation were studied after orthodontic tooth movement for 10 h to 6 days in rats. Defined low or high forces were used. A moderate activity of non-specific alkaline phosphatase was found in the periodontal membrane (PDM) in untreated rats and in rats treated with low forces. In addition, all bone surfaces were outlined with a narrow band of intense non-specific alkaline phosphatase activity that was vanadate- and levamisole-resistant. Likewise, tetracycline was incorporated on all bone surfaces. The bone formation rate was low and uniform within the alveolus, indicating that no intra-alveolar drift of the molar occurred in the untreated rats. Orthodontic forces gradually inhibited vanadate- and levamisole-resistant alkaline phosphatases and tetracycline incorporation on the bone surfaces in the pressure zones of the PDM, depending on the magnitude of the force. It was suggested that the disappearance of these isoenzymes, in a limited area, as seen in the pressure zones, was associated with inhibited bone formation and subsequent initiation of bone resorption. On the tension side a slight reduction and redistribution of vanadate- and levamisole-resistant alkaline phosphatase activity could be noted irrespective of the magnitude of the applied force.

Vanadate and brain adenylate cyclase. Effect of spreading depression

The effect of vanadate on the adenylate cyclase activity of rat cerebral cortex homogenates is described. In the absence of ethyleneglycol-bis-(beta-aminoethyl ether) N,N'-tetraacetic acid (EGTA), 10(-6)M vanadate inhibited enzyme activity by 23%, while 10 (-4) M and 10(-3) M stimulated the enzyme by 14 and 90%, respectively. In the presence of 0.2 mM EGTA, 10 (-6) M to 10(-3) M vanadate had only stimulating effects (18-450%). Additive effects of vanadate and noradrenaline on adenylate cyclase activity suggest different sites of action of these agents. Interaction of vanadate with both fluoride and guanyl-5'-yl imidodiphosphate had an apparently competitive character. Adenylate cyclase maximally stimulated by fluoride (10 mM) was inhibited by vanadate. This inhibitory effect was more pronounced in the absence of EGTA. Adenylate cyclase in the homogenates from the rat cerebral cortex in vivo invaded by spreading depression was slightly increased (up to 38%). This effect was abolished by low (10 (-7) M) vanadate. The results suggest that brain adenylate cyclase is stimulated by vanadate via the guanine nucleotide regulatory protein. The mechanism of vanadate's action, its modulation by calcium ions and the possible physiological role of these effects are discussed.

Effect of vanadium in the +5, +4 and +3 oxidation states on cardiac force of contraction, adenylate cyclase and (Na+ + K+)-ATPase activity

The influence of vanadium in the nominally +5 (NH4VO3; referred to as V5+), +4 (C10H14O5V and VOSO4; V4+) and +3 oxidation states (VCl3; V3+) on cardiac force of contraction, adenylate cyclase and (Na+ + K+)-ATPase activity was investigated in order to determine which form of vanadium mediates the cardiac effects. V5+, V4+ and V3+ (300 microM each) increased the force of contraction of isolated electrically driven cat papillary muscles by about 100%. In the presence of the reducing agent ascorbic acid (5 mM) none of the three compounds led to any distinct increase in force of contraction. On the particulate adenylate cyclase preparation from feline right ventricles only V5+ stimulated the enzyme activity by about 100%, whereas V4+ and V3+ were ineffective. In the presence of 5 mM ascorbic acid all three compounds were ineffective. In contrast, in the presence of the oxidizing agent diamide (azodicarboxylic acid-bis-dimethylamide; 1 mM) all three compounds became stimulatory. On the isolated (Na+ + K+)-ATPase V5+ (500 microM) alone reduced the basal activity by about 95%. In the presence of ascorbic acid the inhibitory effect of V5+ was greatly diminished. Similar results were obtained with V4+, V3+ (100 microM) alone inhibited (Na+ + K+)-ATPase activity only by about 40%. In the presence of ascorbic acid V3+ was ineffective. From the results it is concluded that positive inotropism, stimulation of adenylate cyclase and inhibition of (Na+ + K+)-ATPase by vanadium compounds likewise result from an action of vanadium in the +5 oxidation state.

Plasma vanadium concentration in manic-depressive illness

133 samples of plasma taken from 9 normal control and 8 manic-depressive subjects were analysed for vanadium by atomic absorption spectrometry. Mean plasma vanadium concentrations were 0 . 15 microM in normal control, 0 . 34 microM in manic and 0 . 28 microM in depressed subjects, and 0 . 23 microM in manic-depressive subjects after recovery. The differences between normal subjects and manic and recovered subjects were statistically significant. Significant negative correlations were found between plasma vanadium concentration and the ratio of Na-K-Mg ATPase to Mg-ATPase in 2 manic-depressive subjects, but not in normal subjects. The results suggest that vanadium may be a cause of the variations in Na-K-Mg ATPase and sodium pump activity which are associated with manic-depressive illness.

Vanadium-induced inhibition of renal Na+, K+-adenosinetriphosphatase in the chicken after chronic dietary exposure

Recent work has shown that V accumulates in the kidney and is a potent inhibitor of Na+, K+-adenosinetriphosphatase (ATPase) in vitro. Thus, as a nutritionally required element, V may regulate cation transport. The effect of chronic intake of the metal on Na+, K+-ATPase in vivo has not been reported. In this study laying strain chickens were fed calcium orthovanadate for 15 mo from d 1 of age at levels of 0, 25, 50, and 100 ppm in the diet. Whole tissue homogenates and 13,000 X g fractions were analyzed for ATPase activities. Concentrations of V producing 50% inhibition of Na+, K+-ATPase activity ranged from 1.0 X 10(-5) M in liver to 1.8 X 10(-6) M in kidney, which was the most sensitive tissue tested in vitro. Mg2+ -ATPase was more resistant to V than Na+, K+-ATPase. Studies in vivo suggested a V-dependent inhibition of renal Na+, K+-ATPase. Correlation of enzyme specific activity and levels of V in kidneys suggested V-ATPase mediated alteration in renal function.

Vanadate inhibition of active Ca2+ transport across human red cell membranes

(1) Vanadate (pentavalent vanadium) inhibits with high affinity (K0.5 = 3 microM) the ATP-dependent Ca2+ efflux in reconstituted ghosts from human red cell. (2) To inhibit Ca2+ efflux vanadate has to have access to the inner surface of the cell membrane (3) The inhibitory effect of vanadate is potentiated by intracellular Mg2+ and by intracellular K+. (4) Ca2+ in the external medium antagonizes the inhibitory effect of vanadate.

Vanadate-stimulated NADH oxidation in plasma membrane

The rate of NADH oxidation with oxygen as the acceptor is very low in mouse liver plasma membrane and erythrocyte membrane. When vanadate is added, this rate is stimulated 10- to 20-fold. The absorption spectrum of vanadate does not change with the disappearance of NADH. The reaction is inhibited by superoxide dismutase, and there is no activity under an argon atmosphere. This indicates that oxygen is the electron acceptor and the reaction is mediated by superoxide. The vanadate stimulation is not limited to plasma membrane. Golgi apparatus and endoplasmic reticulum show similar increase in NADH oxidase activity when vanadate is added. The endomembranes have significant vanadate-stimulated activity with both NADH and NADPH. The vanadate-stimulated NADH oxidase in plasma membrane is inhibited by compounds, which inhibit NADH dehydrogenase activity: catechols, anthracycline drugs and manganese. This activity is stimulated by high phosphate and sulfate anion concentrations.

The uptake from fresh water and subsequent clearance of a vanadium burden by the common eel (Anguilla anguilla)

The uptake of 48V vanadium from a solution of 10(-5) M 48V-orthovanadate by fresh-water elvers and the subsequent depletion of the vanadium burden was studied. At the end of the 8-week loading period, the levels of 48V were still increasing in the liver, kidney, bone and carcase. The uptake rate for the whole fish over the 8-week period was 760 pg atom/h/100 g body wt and the depletion rate over the following 5 weeks in clean water was about one tenth of this. Liver contained the highest amount of 48V at the end of the 8-week loading period, calculated as equivalent to 1.1 x 10(-4) g atom V/kg wet wt, and this level was unchanged at the end of the 5-week depletion period. Less than 1% of the carcase 48V was present in the fraction of MW under 2000.

In vivo electrical stimulation alters sensitivity of the brain (Na+ + K+)ATPase toward inhibition by vanadate

It has recently been shown that electrical stimulation of the brain cortex in vivo blocks invasion of cortical spreading depression (SD) into the stimulated area. The effect has been interpreted as a result of activating a K+ pumping mechanism that prevents the accumulation of this ion in the extracellular space to the high levels required for SD propagation. In the present experiments (Na+ + K+)ATPase activity was determined in the electrically stimulated region of the rat brain cortex. When ATP preparations containing vanadate were used as substrate, elevation of K concentration in the assay medium from 2 to 20 mM inhibited enzyme activity in homogenates from the normal cortex but not that from homogenates of the electrically stimulated cortical region. With vanadate-free ATP (Boehringer) as a substrate, slight stimulation by 20 mM K+ has been observed in both cases. Vanadate (0.25 microM) added to the assay medium containing Boehringer ATP and 20 mM K+ inhibited ATPase activity from the normal cortex but not that from the stimulated cortical area. Electrical stimulation may activate (Na+ + K+)ATPase at least partly by diminution of its susceptibility toward the inhibitory action of vanadate.

Effects of orthovanadate on salt and water effluxes from the gills of seawater eels, Anguilla anguilla

Orthovanadate (5 . 10(-7) M) perfused through isolated gills at a constant rate increased the perfusion pressure by 40% but inhibited the effluxes of Na+ and Cl- by 40%. Water efflux was unaltered. Ouabain (10(-4) M) and rotenone (10(-4) M) influenced salt and water effluxes in the same way but did not alter perfusion pressures. Orthovanadate (10(-5) M) perfused at constant rate increased the pressure nearly 2.5-fold; under these conditions effluxes of Na+, Cl- and H2O were all increased approximately 2.5-fold.

Effect of vanadate on myocardial force of contraction

Ammonium vanadate (NH4VO3; 50-1000 microM) increases the force of contraction of isolated electrically driven cat papillary muscles in a concentration-dependent manner. The positive inotropic effect (PIE) of NH4VO3 became significant at 50 microM and was maximal at 500 to 1000 microM. It was accompanied by an increase in the rate of force development, in the rate of relaxation and in relaxation time of the isometric contraction. Similar results as with NH4VO3 were also observed in the presence of 1 microM propranolol, 5 microM phentolamine or after reserpine-pretreatment (5 mg/kg i.p.). These results indicate that vanadate produces a direct PIT in ventricular cardiac muscle which is unlikely to be mediated by alpha- or beta-adrenoceptor stimulation. In cat left atrial strips, however, vanadate ions produced a negative inotropic effect through a hitherto unknown mechanism. Vanadate effects similar to those observed in the cat heart were obtained in ventricular and atrial preparations from bovine hearts.

Vanadate inhibition of the Ca++-ATPase of sarcoplasmic reticulum from pig heart

Ca++-ATPase of sarcoplasmic reticulum from pig heart can be inhibited by vanadate with half maximal inhibition at about 10(-5)M NH4VO3. At the same time vanadate lowers the [Mg++] for maximal activity of the Ca++-ATPase to half, from 8 X 10(-3)M to 4 X 10(-3)M Mg++. At low vanadate concentrations around 5 X 10(-8)M the Ca++-ATPase was activated.

The effect of vanadate on human kidney potassium dependent phosphatase

This study examined the effects of vanadate on the potassium dependent phosphatase activity present in purified human kidney microsomal (Na+ + K+)-adenosine triphosphatase. Vanadate anion inhibited the K+-dependent phosphatase at a K1 of 35 nM. This inhibition was noncompetitive with the substrate, p-nitrophenylphosphate. The inhibition by vanadate at 1 mM K+ was only 45% of the inhibition that was observed at 10 mM K+. Neither preincubation of the enzyme with vanadate, nor changing the pH of the assay from 8.2 to 7.2 had any effect on the K1 for vanadate. The inclusion of 2.5 mM isoproterenol, to complex the yanadate, reversed the inhibition, as did diluting the enzymatic reaction. Vanadate also inhibited the overall (Na+ + K+)-ATPase reaction at a K1 of 1.91 microM. This inhibition was also reversible upon inclusion of isoproterenol in the assay. Increasing the level of magnesium from 6 mM to 30 mM lowered the K1 of vanadate to 0.25 microM. The possible role of vanadate as a physiological mediator of (Na+ + k+)-atpase activity is discussed.