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

Ca-dependent and Mg-dependent ATPase activity was found to be depressed significantly in renal membrane preparations from vitamin D-deficient as compared to normal rats. Administratiin of 2000 i.u. vitamin D2 to deficient rats 30 hours before sacrifice restored the membrane enzyme activity to normal. ATP binding by enzymes was also reduced in vitamin D deficiency and raised by repletion. Vitamin D may therefore be required for normal Ca-and Mg-dependent ATPase activity.
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PMID:Vitamin D -- induced changes in the renal membrane ATPase system. 12 42

The effects of diphenylhydantoin (DPH) and ouabain were studied in vitro on Mg-ATPase, Ca-ATPase and alkaline phosphatase (AlPase) in isolated brush borders from rat jejunum, and in vivo on intestinal calcium absorption. Vitamin D-deficient, -repleted and normal rats were used in this study. Repletion of deficient animals with vitamin D restored Ca-ATPase activity and AlPase activity partly. Ca-absorption was normalized by repletion with the vitamin. DPH greatly stimulated Ca-ATPase activity in vitro and Ca-absorption in vivo, but it inhibited AlPase activity. Mg-ATPase was not affected by vitamin D, nor by DPH. Ouabain had no consistent effect on any of the parameters studied. It was concluded that Ca-ATPase, and not AlPase, is involved in the transport of calcium through the jejunal microvillous membrane, and that DPH enhances Ca-absorption by activation of Ca-ATPase.
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PMID:Stimulation of vitamin D-dependent Ca-ATPase and of intestinal caldium absorption by diphenylhydantoin. 12 71

Dichloromethylene diphosphonate (Cl2MDP) antagonized the action of vitamin D on bone in thyroparathyroidectomized rats by reducing the metabolic activity of osteoblasts and osteocytes and decreasing the number of osteoclasts. Ultrastructurally, osteoblasts in Cl2MDP-treated rats were interpreted to be less active in bone matrix synthesis. Osteocytes in Cl2MDP-treated rats were interpreted ultrastructurally to be inactive; there was no evidence of bone resorption when compared to osteocytes in rats given vitamin D alone. Abnormal osmiophilic densities in the pericellular bone matrix of rats given vitamin D alone were not present in rats given vitamin D and Cl2MDP. The ultrastructure of osteoclasts was unaltered by Cl2MDT. These cellular changes were associated with a decrease in serum calcium and increase in bone ash and magnesium concentration in rats given high levels (10 mg/kg) of Cl2MDP. Bone adenosine triphosphatase and alkaline phosphatase activities were not affected by Cl2MDP. These results suggest that Cl2MDP may limit the hypercalcemia of hypervitaminosis D by directly inhibiting bone cells in addition to its physicochemical action.
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PMID:Interaction of dichloromethylene diphosphonate and vitamin D on bone of thyroparathyroidectomized rats. 14 91

Rats were fed a low calcium diet deficient in vitamin D for 14 days. Changes in alkaline phosphatase activities in odontoblasts dissected out from incisor teeth were studied biochemically. A strong increase in pNPP-ase, PPi-ase, total ATP-degradation and Ca2+- ATPase was observed in the deficient animals compared with animals fed a control diet.
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PMID:Odontoblast metabolism in rats deficient in vitamin D and calcium. II. Changes in activities of alkaline phosphatases. 14 75

The pattern of response of the intestinal enzymes Ca2+-activated adenosine triphosphatase and alkaline phosphatase in the chick to 1,25-dihydroxycholecalciferol is consistent with a role for the former but not the latter enzyme in the vitamin D-dependent absorption of calcium.
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PMID:Differentiation of the changes in alkaline phosphatase from calcium ion-activated adenosine triphosphatase activities associated with increased calcium absorption in chick intestine. 15 34

Purified porcine erythrocyte membrane Ca(2+)-ATPase and 3':5'-cyclic nucleotide phosphodiesterase were stimulated in a dose-dependent, saturable manner with the vitamin D-dependent calcium binding protein from rat kidney, calbindin-D28k (CaBP-D28k). The concentration of CaBP-D28k required for half-maximal activation (K0.5 act.) of the Ca(2+)-ATPase was 28 nM compared to 2.2 nM for calmodulin (CaM), with maximal activation equivalent upon addition of either excess CaM or CaBP-D28k. 3':5'-Cyclic nucleotide phosphodiesterase (PDE) also showed equivalent maximum saturable activation by calbindin (K0.5 act. = 90 nM) or calmodulin (K0.5 act. = 1.2 nM). CaBP-D28k was shown to effectively compete with CaM-Sepharose for PDE binding. Immunoprecipitation with CaBP-D28k antiserum completely inhibited calbindin-mediated activation of PDE but had no effect on calmodulin's ability to activate PDE. While the physiological significance of these results remains to be established, they do suggest that CaBP-D28k can activate enzymes and may be a regulator of yet to be identified target enzymes in certain tissues.
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PMID:In vitro enzyme activation with calbindin-D28k, the vitamin D-dependent 28 kDa calcium binding protein. 131 45

The mechanism of vitamin D-dependent intestinal calcium transport has been explored in experimental animals in vivo and in vitro with the aid of pharmacologic agents that inhibit steps in the translocation process. Glucocorticoids in vivo, but not in vitro, inhibit the mucosal-to-serosal flux (Jms) of calcium and thus reduce net calcium absorption. Chronic metabolic acidosis inhibits calcium transport in vivo through inhibition of 1,25-dihydroxycholecalciferol [1,25(OH)2D3] production and by a direct effect in vitro on the enterocyte to decrease calcium Jms. Cellular functions that may be involved in the transport process have been inhibited in vitro, including brush border calcium uptake by calcium channel blockers; calmodulin-dependent Ca-activated ATPase by trifluoperazine; calcium binding to vitamin D-dependent calcium-binding protein (CaBP, calbindin) by theophylline and acidic lysosomal vesicle function by quinacrine, chloroquine and ammonium chloride. The results of these studies demonstrate the consequences of selectively inhibiting steps thought to be involved in calcium transport and suggest new directions for further research in elucidating mechanisms of cellular calcium transport.
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PMID:The use of pharmacologic agents to study mechanisms of intestinal calcium transport. 154 31

Vitamin D3 undergoes sequential hydroxylations in the liver and kidney to form 1,25-dihydroxyvitamin D3, the biologically active form of the vitamin. 1,25-dihydroxyvitamin D3 is metabolized by several processes in various target tissues that decrease the biological activity of the sterol. In addition, 1,25-dihydroxyvitamin D3 is excreted in the bile as polar metabolites, such as glucuronides and, possibly sulfates and neutral polar steroids. These compounds undergo an enterohepatic recirculation in both man and experimental animals. 1,25-dihydroxyvitamin D3 increases the absorption of calcium in the intestine and the reabsorption of calcium in the kidney. It induces the synthesis of several proteins, the most notable of which is calcium binding protein that is thought to play a role in the absorption of calcium. The vitamin D-dependent calcium binding proteins and the calcium-magnesium ATPase calcium pump are co-localized in several tissues that play a role in the absorption of calcium.
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PMID:Vitamin D metabolism and mechanisms of calcium transport. 210 49

The process of insulin release evoked by D-glucose and other nutrient secretagogues is triggered by an increase in cytosolic Ca2+ activity. However, some other insulinotropic agents may stimulate insulin release at a close-to-basal concentration of cytosolic ionized calcium. The control of cytosolic Ca2+ concentration depends not solely on the rate of Ca2+ entry into the cell through voltage-sensitive channels and Ca2+ exit via Na(+)-Ca2+ countertransport or active Ca2+ pumping, but also on the subcellular distribution of Ca2+, as dependent, for instance, on both Ca2(+)-ATPase activity and inositol 1,4,5-triphosphate-sensitive release in microsomes and calcium accumulation in mitochondria. Calmodulin and calbindin were both identified in pancreatic islet cells. Activation of adenylate cyclase by calcium-calmodulin may account for the increased production of cyclic AMP in islets stimulated by nutrient secretagogues. Calbindin is present in both normal and tumoral islet cells, and might participate to the alteration of islet function encountered in vitamin D-deprived or repleted rats. However, no target enzyme for calbindin was yet identified in islet cells. Independently of the role of calcium-binding regulatory proteins, the mitochondrial accumulation of calcium may account in part at least, for the preferential stimulation of mitochondrial oxidative events in the process of nutrient-stimulated insulin release.
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PMID:Calmodulin and calbindin in pancreatic islet cells. 219 50

The active calcium transport process in the intestine is transcellular. Entry across the brush border of the enterocyte is down an electrochemical gradient, probably via calcium channels. The entry process, although modified by vitamin D, does not appear to be the rate-limiting step, as total vitamin D deficiency lowers the rate of entry only by about a third, whereas active calcium transport is wholly inhibited. Calcium extrusion is effected by the Ca-ATPase, is against an electrochemical gradient, and requires a supply of energy. However, it is not the rate-limiting step, as extrusion capacity is more than sufficient to handle the maximum transcellular flux of calcium. It is the flow of calcium inside the cell, from the brush-border pole to the pump at the basolateral side, that is rate-limiting. Basal calcium flow, in the absence of the cytosolic, vitamin D-dependent calcium-binding protein, CaBP, is only about 1/70 of the maximum rate, Vm, in the vitamin D-replete duodenum. CaBP levels vary linearly with the Vm. Moreover, interference with calcium binding by CaBP interferes with active calcium transport. Active calcium transport is totally regulated by vitamin D or processes that modify the action or metabolism of the sterol. Since, however, active calcium transport is only one of the two routes of calcium absorption, the other being a passive, paracellular process, up- or down-regulation of active transport may have only a limited effect on total calcium absorption.
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PMID:Intestinal calcium transport: the cellular pathway. 225 Jun 26


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