Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat striatal synaptosomes (P2-fraction) were subjected to lipoperoxidation by the addition of 120 microM Fe2+ and 200 microM ascorbic acid. This preparation (pretreated synaptosomes) was used to investigate the interaction of Pb2+ and Mn2+ on the uptake of tritiated catecholamines, Na+, K+-ATPase activity and malondialdehyde (MDA) formation in order to understand the mechanism of enhanced neurotoxicity by concurrent exposure to these metals. The combination of Pb2+ and Mn2+ (25 microM + 100 microM, respectively) produced a significant increase in the uptake of 3H-Dopamine only in the untreated synaptosomes. No significant effect was noted on the uptake of 3H-Norepinephrine in either pretreated or untreated synaptosomes. However, the combination of Pb2+ and Mn2+ produced a pronounced decrease in the activity of Na+, K+-ATPase, but the magnitude of the change was the sum of the individual metal effects. Metal interaction did not produce any significant change in the formation of MDA compared to the control (without addition of metals). These results indicate that Pb2+ and Mn2+ interaction may produce inhibition in the activity of transport ATPase in both the preparation of synaptosomes, with more pronounced effect of synaptosomes subjected to lipoperoxidation and these changes may be responsible for the disruption in the physiology of nerve impulse transmission.
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PMID:The combined effect of Pb2+ and Mn2+ on monoamine uptake and Na+, K+-ATPase in striatal synaptosomes. 304 Aug 46

Ascorbic acid and Mg-ATP were found to regulate norepinephrine biosynthesis in intact secretory vesicles synergistically and specifically, using the model system of isolated bovine chromaffin granules. Dopamine uptake into chromaffin granules was shown to be unrelated to the presence of Mg-ATP and ascorbic acid at external dopamine concentrations of 7.5 and 10 mM. Under these conditions of dopamine uptake, norepinephrine biosynthesis was enhanced 5-6-fold by Mg-ATP and ascorbic acid compared to control experiments with dopamine only. Furthermore, norepinephrine formation was enhanced approximately 3-fold by ascorbic acid and Mg-ATP together compared to norepinephrine formation in granules incubated with either substance alone. The action of Mg-ATP and ascorbic acid together was synergistic and independent of dopamine content of chromaffin granules as well as of dopamine uptake. The apparent Km of norepinephrine formation for external ascorbic acid was 376 microM and for external Mg-ATP was 132 microM, consistent with the larger amounts of cytosolic ascorbic acid and ATP that are available to chromaffin granules. Other physiologic reducing agents were not able to increase norepinephrine biosynthesis in the presence or absence of Mg-ATP. In addition, maximum enhancement of norepinephrine biosynthesis occurred only with the nucleotide ATP and the cation magnesium. The mechanism of the effect of ascorbic acid and Mg-ATP on norepinephrine biosynthesis was investigated and appeared to be independent of a positive membrane potential. The effect was also not mediated by direct action of ADP, ATP, or magnesium on the activity of soluble or particulate dopamine beta-monooxygenase. These data indicate that Mg-ATP and ascorbic acid specifically and synergistically co-regulate dopamine beta-monooxygenase activity in intact chromaffin granules, independent of substrate uptake. Although the mechanism is not known, the data are consistent with the possibility that the chromaffin granule ATPase mediates these effects.
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PMID:Ascorbic acid and Mg-ATP co-regulate dopamine beta-monooxygenase activity in intact chromaffin granules. 314 26

Although dopamine is known to be natriuretic, it is not clear if this is due to changes in renal hemodynamics or to a direct tubular effect. Studies on the effect of dopamine on proximal sodium reabsorption have yielded conflicting information, both an increase and a decrease in sodium reabsorption has been reported. The present study examines the direct effect of dopamine on sodium uptake in proximal renal cells and the possible mechanisms involved. Dopamine (10(-7)-10(-4) M) stimulated in a dose-dependent manner sodium uptake by proximal renal cells by 35-92%; 1 mM ouabain and 70 microM cycloheximide did not modify the effect of dopamine. Kinetic analysis of sodium uptake by these cells showed a single saturable component, inhibitable by amiloride, with a Km of 80 +/- 6 mM and Vmax of 68 +/- 9 pmol/mg protein/min. Dopamine (10(-4) M) increased the Vmax of sodium uptake by 54 +/- 10.3% and had no effect on the Km. Metoclopramide abolished the stimulatory effect of dopamine on sodium uptake whereas propranolol had no effect. Epinine (a dopamine agonist) also stimulated sodium uptake by these cells. We conclude that dopamine directly stimulates sodium uptake in proximal renal cells; this suggests the natriuretic effect of dopamine in whole animals is due to changes in renal hemodynamics and distal tubular effects; dopamine increases the Vmax of the sodium transporter and not the Km; the sensitivity of sodium uptake to amiloride suggests that dopamine stimulates Na+-H+ exchanger, and the stimulation of sodium uptake by dopamine is independent of Na+-K+-ATPase and new protein synthesis and occurs via the dopamine receptor.
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PMID:Effect of dopamine on sodium uptake by renal proximal tubule cells of rabbit. 380 28

1. Homogenates of bovine splenic nerves were subjected to differential and sucrose density gradient centrifugation. From the low-speed supernatant a high-speed sediment (mitochondria, lysosomes, microsomes and noradrenaline (NA) vesicles) was obtained. By density gradient centrifugation of this sediment it was shown that NA vesicles are slightly less dense than mitochondria, but denser than microsomes.2. In further experiments a mitochondrial and a microsomal sediment were obtained. The mitochondrial sediment was fractionated with a short centrifugation time over a density gradient ranging from 0.6 to 1.2 M sucrose. Mitochondria (fumarase and succinate-dehydrogenase) and lysosomes (acid ribonuclease and deoxyribonuclease) sedimented to the bottom of the tube. The highest concentration of NA vesicles was found in a medium position. There was only a small amount of microsomes (glucose-6-phosphatase) present.3. The microsomal sediment was centrifuged for 150 min over a density gradient ranging from 0.8 to 1.4 M sucrose. The microsomes remained on the top of the gradient. There were also some mitochondria and lysosomes present. The NA vesicles were found in highest concentration in the middle of the gradient (at about 1.2 M sucrose).4. With the use of these two density gradients, the subcellular distribution of dopamine-beta-hydroxylase, monoamine oxidase and ATPase was studied. Dopamine-beta-hydroxylase was found to be localized in the NA vesicles. Monoamine oxidase was mainly recovered in mitochondria; a small part of the enzyme appeared to be microsomal. ATPase was present in microsomal elements.
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PMID:Bovine splenic nerve: characterization of noradrenaline-containing vesicles and other cell organelles by density gradient centrifugation. 431 May 9

Washed membranes of bovine adrenal chromaffin granules contained most of the cholesterol and phospholipids of the particle and 22% of the total protein. The protein/lipid ratio was about 0.45 (w/w). Dopamine(3,4-dihydroxyphenethylamine)beta-hydroxylase, Mg(2+)-activated nucleoside triphosphatase and cytochrome b-559 activities were present in the membrane. ATP was the best substrate for the nucleoside triphosphatase, whose pH optimum was 6.4, K(m) 7x10(-4)m and V(max.) 1.8mumol/h per mg of protein. Treatment of the membranes with various detergents caused a preferential solubilization of protein compared with lipids. Membranes dissolved in sodium dodecyl sulphate or phenol-acetic acid-urea were subjected to polyacrylamide-gel electrophoresis at alkaline and acid pH respectively. The electrophoretic patterns given by the proteins of the chromaffin granule membrane were distinct from those given by the chromogranins, and from those given by mitochondrial and microsomal membrane proteins.
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PMID:Membranes of the adrenal medulla. Behaviour of insoluble proteins of chromaffin granules on gel electrophoresis. 432 Aug 20

Dopamine inhibits Mg2+,Na+,K+- and Na+,K+-ATPase activities but does not modify Mg2+-ATPase activity of nerve ending membranes isolated from rat cerebral cortex. In the presence of the soluble fraction of brain, dopamine activates total, Na+,K+-, and Mg2+-ATPases. Dopamine stimulation of nerve ending membrane ATPases is achieved when soluble fractions of brain, kidney, or liver are used. On the other hand, dopamine effects are not observed on kidney or heart ATPase preparations. The results indicate tissue specificity of dopamine effect with respect to the enzyme source; there is no tissue specificity for the requirement of the soluble fraction to achieve stimulation of ATPases by dopamine.
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PMID:Tissue specificity of dopamine effects on brain ATPases. 611 33

Specific effects of various catecholamines as well as functional dependence of mitochondrial enzymes activity on catecholamine metabolism were studied. Dopamine activated cytochrome c oxidase in heart mitochondria and decreased this enzymatic activity in liver tissue. Noradrenaline and adrenaline activated cytochrome c oxidase in liver, brain and kidney tissues. The effect of dopamine on cytochrome c oxidase was prevented by activation of dopamine beta-hydroxylase. Increased activity of monoamine oxidase caused accumulation of catecholamine metabolites, which inhibited the succinate dehydrogenase activity in liver tissue and the cytochrome c oxidase activity in brain, kidney and liver tissues. In the catecholamine regulation of succinate dehydrogenase and ATPase activities in all the tissues studied as well as of cytochrome c oxidase activity in heart tissue the quinoid oxidation products were apparently involved.
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PMID:[Catecholamine metabolism and mitochondrial enzyme activity]. 612 94

The effects of dopamine agonists and antagonists on the Na+,K+-ATPase and Mg2+-ATPase activities of rat cerebral cortex synaptosomes have been determined. Dopamine, ADTN, apomorphine and S-584, but not piribedil, stimulated the activities of the enzymes. The stimulatory effect of dopamine was not antagonised by dopamine antagonists and apparently the catechol group is responsible for the enzyme stimulation.
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PMID:The effects of dopamine agonists and antagonists on Na+,K+-ATPase and Mg2+-ATPase activities of synaptosomes. 612 58

A proton-translocating adenosinetriphosphatase in adrenal medullary chromaffin granule ghosts can generate either a membrane potential (inside positive) or a pH gradient (inside acid). Dopamine uptake occurs in response to both the membrane potential and the pH gradient. The natural logarithm of the dopamine concentration gradient [In (Din/Dout)] is linearly related to the membrane potential with a slope of F/(RT). This dependence is not affected by the pH of the medium. In (Din/Dout) is linearly dependent on In ([H+]in/[H+]out) with a slope of 2. These results indicate that dopamine is taken up via an exchange diffusion or antiport mechanism. The stoichiometry of this exchange is two H+/dopamine cation and is independent of pH.
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PMID:Stoichiometry of H+-linked dopamine transport in chromaffin granule ghosts. 645 32

Dopamine decreases tubular sodium reabsorption, attributed in part to Na-K-ATPase inhibition in the proximal convoluted tubule (PCT). Because the final regulation of sodium excretion occurs in the collecting duct, where specific dopamine DA1 binding sites have been demonstrated, we examined the effects of dopamine, as well as of DA1 and DA2 receptor agonists on Na-K-ATPase activity and on the number of units in Madin-Darby canine kidney (MDCK) cells, which retain differentiated properties of the renal cortical collecting tubule epithelium. Dopamine (10(-5) M) inhibited pump activity (by 50%) and reduced the number of units. This effect was reproduced by the DA1 agonist SKF 38393, which inhibited pump activity in a dose- and time-dependent manner (maximum, 10(-5) M). The DA2 agonist quinpirole hydrochloride was without effect, either alone or in combination with SKF 38393. Inhibition of pump activity by dopamine was totally abolished by H7 (100 microM), an inhibitor of protein kinase (PK), but partially by 2',5'-dideoxy-adenosine (DDA) and H4, respective inhibitors of cAMP production and PKA, which suggests that the dopamine effect on Na-K-ATPase activity may be linked to activation of both PKC and PKA. In these cells, amiloride addition during preincubation did not alter the effect of dopamine on Na-K-ATPase activity; in contrast, furosemide increased further the inhibitory effect of dopamine on the enzyme activity. Monensin addition (10(-3) M) reversed the inhibitory effect of dopamine after a 30-min preincubation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mechanisms of dopamine effects on Na-K-ATPase activity in Madin-Darby canine kidney (MDCK) epithelial cells. 754 25


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