Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.1 (alkaline phosphatase)
 47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Renal epithelial function, proton flux and sodium stimulated proton flux, was observed in vesicles isolated from the brush border of the proximal tubule of Sockeye Salmon (Oncorhynchus nerka) during migration. Brush border membrane vesicles (BBMV) were isolated from the body kidney of Sockeye Salmon using aggregation/differential centrifugation techniques. Vesicle purity was tested using a series of epithelial and basal lateral markers including alkaline phosphatase, maltase, gamma-glutamyl transferase (GGTP), Mg(2+)-activated ATP-ase, Na(+)+K(+)-activated ATPase, and 5'-nucleotidase and the lysosomal marker acid phosphatase. An enrichment/depletion factor for each marker was determined by comparison of purified BBMV with kidney homogenate. Vesicles exhibit an enrichment factor for alkaline phosphatase, GGTP, maltase, Mg(2+)-activated ATP-ase, Na(+)+K(+)-activated ATPase, and 5'-nucleotidase. A depletion factor was observed for acid phosphatase. Vesicle integrity was tested by measuring the time course of proton flux in the presence of a pH gradient. Amiloride sensitive sodium stimulated proton flux was observed in these vesicles. The presence of sodium caused a saturable increase in the rate of proton flux, indicating the activity of a sodium/proton antiport protein in BBMV.
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PMID:Proton transport and Na+/H+ exchange in vesicles isolated from sockeye salmon (Oncorhynchus nerka) kidneys during migration from salt to fresh water. 132 4

Chronic hypercapnia is associated with increased proximal HCO3 reabsorption that is thought to be mediated by a Na-H antiporter. We hypothesized that chronic hypercapnia would be associated either with increased Vmax or with decreased Km of the Na-H antiporter. To test this hypothesis we made rabbits hypercapnic for 48 h by exposure to 10% CO2. In both control and hypercapnic animals, cortical luminal membranes were enriched over the homogenate 16-fold in alkaline phosphatase and 10-fold in maltase activity. The kinetic activity of the Na-H antiporter was measured by the dissipation of the quenching of acridine orange by addition of different Na concentrations. Chronic hypercapnic rabbits had significantly higher Vmax of the Na-H antiporter of luminal membranes than controls (593 +/- 81 vs. 252 +/- 40 arbitrary fluorescence units X min-1 X 300 micrograms protein-1, P less than 0.01). The Km, however, was not different between control and hypercapnic rabbits. 22Na uptake in presence of an outwardly directed pH gradient was significantly higher in vesicles from hypercapnic rabbits than controls. Amiloride inhibited the Na-H antiporter (as assessed by acridine orange quenching or 22Na uptake) to the same degree in membranes from both control and hypercapnic rabbits, suggesting that the increase in Vmax is mediated by the electroneutral component of the Na-H antiporter. In addition, under voltage clamp conditions by K and valinomycin the Vmax was still increased in membranes from hypercapnic animals, again suggesting that the increase in Vmax is mediated by the electroneutral component of the Na-H antiporter. The uptake of D-[3H]glucose by luminal membranes was not different between control and hypercapnic rabbits, indicating a specific enhancement of the Na-H antiporter. Acute hypercapnia (4 h) failed to increase the Vmax of the Na-H antiporter despite comparable increase in PCO2. Thus chronic hypercapnia, but not acute hypercapnia, induces a selective and specific increase in the Vmax of Na-H antiporter, and this may mediate the adaptation to chronic hypercapnia.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Chronic hypercapnia enhances Vmax of Na-H antiporter of renal brush-border membranes. 282 Feb 41

We divided 36 male pathogen-free Sprague-Dawley rats with an average live mass (LM) of 51 g into four treatment groups of nine animals each. They received for a period of 28 trial days a semisynthetic purified diet based on casein for ad libitum consumption, supplemented with 5 ppm zinc (groups 1-3) or 57 ppm zinc (group 4) as zinc sulfate. In addition to the diet, groups 2 and 3 were given a diuretic supplement of amiloride at the therapeutic dose rate (0.4 mg amiloride/kg LM0.75 per day) or in a dosage corresponding to the chronic toxicity level (maximum tolerated dose; 0.8 mg amiloride/kg LM0.75 per day). The supplementation with amiloride, acting as a potential Zn-binding ligand at the selected dosage levels, had no influence on the animals' live weight during the 28-day trial period; weight gain was determined solely by the dietary Zn concentration. Amiloride administered at the therapeutic or the maximum tolerated dose produced no evidence of a diminished Zn status in terms of the alkaline phosphatase activity in the serum or the Zn concentration in the serum, femur and testes. Medication with amiloride at the maximum tolerated dose even exerted a positive effect on the zinc supply status as demonstrated by the raised Zn concentration in the serum. This suggests that zinc supplementation may not be required during medication with amiloride in human medicine.
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PMID:Influence of dietary amiloride supplement on the zinc status of growing rats with marginal zinc supply. 852 74

Purified basolateral membrane vesicles (BLMVs) were prepared from Atlantic lobster (Homarus americanus) hepatopancreas using a Percoll density gradient technique. Enrichments of the Na+/K+-ATPase and alkaline phosphatase activities of these vesicles were 15.4- and 1.2-fold, respectively. The presence of amiloride-sensitive Na+/H+ exchange was demonstrated. Contrary to electrogenic 2Na+/1H+ exchange on apical membranes from the same tissue, kinetic studies of Na+ transport by these basolateral membranes indicate an electroneutral antiport with a Km of 28±1.7 mmol l-1 and a Jmax of 1.74±0.13 µmol mg-1 min-1. Amiloride interacted at a single binding site (Ki=39 µmol l-1) and external Li+ was shown to be an effective competitive inhibitor of the exchange process (Ki=493 µmol l-1). The presence of a membrane-potential-sensitive, Na+-accepting ion channel was also demonstrated. The basolateral Na+/H+ exchanger physiologically resembles members of the NHE family of Na+/H+ antiporters described in vertebrates and departs from the apical electrogenic system previously described in lobster. Whether or not the basolateral Na+/H+ antiporter is an NHE isoform remains to be determined.
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PMID:Characterization of a basolateral electroneutral Na+/H+ antiporter in Atlantic lobster (Homarus americanus) hepatopancreatic epithelial vesicles 931 72

Little is known about the function of acid-sensing ion channels (ASICs) in bone cells or osteoporotic vertebral fractures (OVF). This study delineated ASICs expression in adult human bone marrow-mesenchymal stem cells- (BM-MSC-) derived osteoblasts and in OVF bone cells. Adult BM-MSC-derived osteoblasts were isolated and cultured in different pH values. Osteogenic markers as alkaline phosphatase (ALP), osteopontin (OPN), and osteocalcin (OC) mRNA were assessed. Western blots method was applied to analyze ASICs protein expression in different pH values. Amiloride was added into the osteogenic media to analyze the Na+/K+ ATPase change. We harvested the vertebral cancellous bone through a bone biopsy needle in 26 OVF patients when performing percutaneous vertebroplasty. Six vertebral bone specimens obtained from 4 patients with high-energy vertebral fractures were used as the control. The reverse transcription polymerase chain reaction was performed to analyze the quantitative mRNA expression of ASICs. Osteogenic markers as ALP, OPN, and OC mRNA were higher expressed in increasing pH values throughout osteoblastogenesis. ASIC proteins were higher expressed in lower pH media, especially ASIC3, and ASIC4. The highest protein expression at days 7, 14, and 21 was ASIC2, ASIC4, and ASIC3, respectively. Expression of Na+/K+ ATPase was significantly decreased in cultured osteoblasts by addition of amiloride into the pH 6.9 osteogenic media. ASIC2 mRNA was most highly expressed with a 65.93-fold increase in the biopsied vertebral bone cells in OVF compared with the control. In conclusion, we found osteoblastogenesis was reduced in an acidic environment, and ASIC2, ASIC3, and ASIC4 were most highly expressed in turn during osteoblastogenesis within acidic media. ASIC2 was the most abundantly expressed gene in human bone cells in OVF compared with the control. ASIC2 could be crucial in the pathogenesis of osteoporosis and could serve as a therapeutic target for antiosteoporotic therapies.
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PMID:High Expression of Acid-Sensing Ion Channel 2 (ASIC2) in Bone Cells in Osteoporotic Vertebral Fractures. 3153 54