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)

The present study was designed to test whether tubular carbon dioxide production from the carbon skeleton of uniformly 14C-labelled glutamine exhibits quantitative and qualitative segmental heterogeneity. Our results show that CO2 production from glutamine in the proximal convoluted tubule (PCT) was dependent on substrate concentrations and is saturable at 10(-4) M of glutamine. Glutamine oxidation was demonstrable in all nephron segments examined. The PCT is the quantitatively predominant site of glutamine oxidation. Intermediate nephron segments, however, such as the thick ascending limb (MAL) and the distal convoluted tubule possess a significant capacity for glutamine oxidation, particularly when examined in terms of tubular protein content. Modulation of glutamine oxidation by extracellular pH was segment specific. Stimulation by acidosis and inhibition by alkalosis were observed in the PCT while carbon dioxide production from glutamine in the MAL was pH-insensitive. Glutamine oxidation was closely linked to sodium transport and greatly decreased by inhibition of Na-K-ATPase. In both the PCT and MAL, glutamine oxidation was inhibited by high extracellular potassium concentrations and in the PCT enhanced by extracellular hypokalemia. N-Ethyl maleiamide, an inhibitor of proton ATPase, led to almost complete cessation of CO2 production from the substrate in both PCT and MAL. Acetazolamide, an inhibitor of carbonic anhydrase, led to a partial reduction in carbon dioxide formation in the PCT, but did not affect glutamine oxidation in the MAL. We conclude that segmental qualitative heterogeneity characterizes oxidation of the carbon skeleton of glutamine with proximal segments showing the predictable effects of pH changes and carbonic anhydrase inhibition. The MAL appears to be nonmodulating.
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PMID:Tubular CO2 production from glutamine in the rat: segmental profile and modulation. 137 65

In this report, we describe the fractionation of crude axolemmal fractions from rat lower brainstem into subfractions enriched in markers for either periaxolemmal myelin or axolemma. These subfractions were isolated on density gradients as bands layering on 0.8M and 1.0M sucrose. Both subfractions consisted of unilamellar vesicles. Relative to myelin purified from the same starting material, the 0.8M subfraction was enriched in MAG, CNPase, carbonic anhydrase and Na+, K+ ATPase but was extremely low in PLP and MBP. In addition, this fraction exhibited a protein profile distinct from myelin. The 1.0M fraction was also highly enriched in Na+, K+ ATPase and had an overall composition similar to the 0.8M subfraction. However, it differed from the 0.8M subfraction by being low in MAG, CNPase, and carbonic anhydrase, but enriched in voltage-dependent Na+ channel, axon-specific fodrin, and MAP-1B. Based on these characteristics we concluded that the 0.8M and 1.0M subfractions were highly enriched in periaxolemmal myelin and axolemmal membrane, respectively. Plasmolipin10 was unique with equally high levels in myelin and in the 0.8M and 1.0M subfractions. Both subfractions were enriched, relative to myelin, in the alpha subunit of the GTP binding protein, Go, and the alpha subunit common to all G proteins, GA/1. Electrophysiology with membrane subfractions fused to lipid bilayers showed that both membranes contained sets of K+ and Cl- channels, which based on channel sizes and open times, are largely distinct from one another.
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PMID:Isolation and characterization of periaxolemmal and axolemmal enriched membrane fractions from the rat central nervous system. 138 38

pH regulatory mechanisms in primary cultures of astrocytes from the cerebral cortex of neonatal audiogenic-seizure-susceptible DBA/2J (DBA) and genetically controlled C57BL/6J (C57) mice were studied with [14C]dimethyloxazolidine-2-4-dione (DMO) and [3H]-methyl-D-glucose (MDG). Effects of changing the concentration of Na+, K+, HCO3- or Cl- in medium, and/or of different transport blockers and metabolite inhibitor on intracellular pH (pHi) of cultured astrocytes were also studied. In nominal HCO3(-)-free HEPES-buffered Hanks' balanced salt solution (HEPES HBSS), when the pH of medium (pHo) was maintained at 7.4, the steady-state pHi of cultured astrocytes from DBA mice was 6.98 +/- 0.03, and that from C57 mice was 7.01 +/- 0.03. When the cells were incubated in HBSS containing 25 mM HCO3- and equilibrated with 5% CO2 (HCO3- HBSS, pHo = 7.4), pHi of both DBA and C57 astrocytes was approximately 0.1-0.15 pH units higher than that in HEPES HBSS. Reducing the pH or the Na+ concentration in media (pHo, [Na+]o) of either HEPES HBSS or HCO3- HBSS, pHi of both DBA and C57 astrocytes decreased markedly (0.25-0.45 pH units lower than the controls). The decrease in pHi was greater in HEPES HBSS than in HCO3- HBSS. Reducing the Cl- concentration ([Cl-]o) in either HEPES or HCO3- HBSS, pHi of astrocytes increased by 0.05-0.1 pH units. Increasing the K+ concentration ([K+]o) of or adding Ba2+ to the media increased the pHi of both DBA and C57 astrocytes accordingly. SITS, an anion transport inhibitor, decreased the pHi of both DBA and C57 astrocytes in HCO3- HBSS but not in HEPES HBSS. It enhanced the response of pHi to reduction in pHo. Amiloride, a Na(+)-H+ exchange inhibitor, decreased the pHi of both DBA and C57 astrocytes more in HEPES HBSS than in HCO3- HBSS. It enhanced the response of pHi to reduction in pHo and [Na+]o. Ouabain, an Na+,K(+)-ATPase inhibitor, decreased the pHi of cultured astrocytes in HEPES HBSS, but not in HCO3- HBSS. It also enhanced the response of pHi to changing pHo and [Na+]o in HEPES HBSS. Acetazolamide, a carbonic anhydrase inhibitor, decreased the pHi of astrocytes in both HEPES and HCO3- HBSS. Both bumetanide, an Na+,K+/Cl- cotransport blocker, and KCN, a metabolic inhibitor, produced no significant effect on the steady-state pHi or the response of pHi to changing ionic concentration in media in both DBA and C57 astrocytes.
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PMID:Studies on pH regulatory mechanisms in cultured astrocytes of DBA and C57 mice. 139 16

Acidification of the luminal fluid in the epididymis is believed to play an important role in sperm maturation. Previous studies have shown that specialized cells in the epithelium lining the epididymis contain high levels of carbonic anhydrase and that these cells have rod-shaped intramembraneous particles when examined by freeze fracture. Both of these features are characteristic of proton-transporting intercalated cells in the kidney collecting duct. We now show that apical cells in the head of the epididymis and clear cells in the body and tail of the epididymis express high levels of a vacuolar proton-pumping adenosinetriphosphatase on their apical plasma membranes and on intracellular vesicles. By analogy with kidney intercalated cells, these cell types may be specialized for acid secretion in the epididymis.
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PMID:A plasma membrane proton ATPase in specialized cells of rat epididymis. 141 77

The concentration of calcium-binding protein (CaBP) and the activities of calcium adenosine triphosphatase (Ca(2+)-ATPase) and carbonic anhydrase (CA) were determined in the shell gland mucosa of hens in two experiments. In Experiment 1, laying hens on a proprietary layer mash were compared with hens rested from lay by the feeding of whole grain barley. In Experiment 2 comparisons were made of laying hens fed the proprietary layer mash and producing eggs with either strong or weak shells. These latter comparisons were also made when the shell gland was quiescent or active with respect to daily eggshell formation. Feeding whole grain barley reduced egg production to zero after 11 days. This reduction in rate of lay was accompanied by significant reductions in all three markers, the effect on Ca(2+)-ATPase and CaBP being less than for CA. Control values were regained between 10 and 16 days after the barley was replaced with the layer mash. Relative shell strength and the physiological status of the shell gland with respect to time of daily eggshell formation had no significant effect on any marker in Experiment 2.
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PMID:Calcium and carbonate supply in the shell gland of hens laying eggs with strong and weak shells and during and after a rest from lay. 147 May 88

A rat kidney- and intestine-specific cDNA (D2) that induces high-affinity, Na(+)-independent uptake of cystine and dibasic and neutral amino acids into cRNA-injected Xenopus oocytes was recently isolated by expression cloning in our laboratory (R. G. Wells and M. A. Hediger. Proc. Natl. Acad. Sci. USA 89: 5596-5600, 1992). At present it is not known whether the D2-encoded protein functions as a transporter or as a transporter activator. To gain more insight into the role of D2 in renal amino acid transport, we studied the site of its expression in the kidney. This was determined by Northern blot analysis and by using a combination of in situ hybridization and immunocytochemistry with antibodies that recognize specific proximal tubule segments. D2 antisense RNA hybridized to the same tubular segments that were strongly positive for anti-ecto-adenosinetriphosphatase but negative for carbonic anhydrase type IV and the facilitated glucose transporter GLUT2. We conclude that D2 mRNA is strongly expressed in the rat kidney proximal tubule S3 segment, although there is weak hybridization to the S1 and S2 segments. The signal is absent in all other parts of the kidney. The S3 specific expression of D2 mRNA coincides with the site of high-affinity transport of cystine and other amino acids, consistent with the proposed involvement of D2 in these processes.
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PMID:Expression of mRNA (D2) encoding a protein involved in amino acid transport in S3 proximal tubule. 148 85

The frog skin in vivo is capable of active transepithelial H+ secretion (JH) which is matched by Na+ absorption (JNa). Studies in vitro demonstrate that JH is generated by an H(+)-ATPase pump localized in apical membranes of mitochondria-rich (MR) cells, whereas JNa occurs through an amiloride-sensitive pathway in principal (P) cells. The H+ pump is sensitive to inhibitors of carbonic anhydrase (e.g. acetazolamide) and to specific inhibitors of mitochondrial F1F0 H(+)-ATPase (oligomycin) and vacuolar (V)-type H(+)-ATPase (N-ethylmaleimide) and to inhibitors of both these types of H(+)-ATPases (dicyclohexylcarbodiimide, DCCD). JH is independent of external K+, which differentiates it from gastric H+/K(+)-ATPase and is strictly dependent on aerobic metabolism. The proton pump is primarily implicated in whole-body acid-base regulation. Acute stimulation of JH in response (seconds-minutes) to an acid load involves insertion of H+ pumps (exocytosis) from a cytosolic pool into the apical membrane. The chronic response (days) to metabolic acid load involves morphological changes (increased apical membrane surface area and number of MR cells). Whole-cell patch-clamp recordings of membrane capacitance and current fluctuations from MR cells demonstrate that a respiratory acid load and aldosterone produce rapid exocytotic insertion of DCCD-sensitive conductive membrane. A secondary role of the H+ pump is to energize sodium absorption (JNa) via principal cells from dilute solutions in the absence of a permeant anion under open-circuit conditions. The apparent 1:1 stoichiometry between JH and JNa is a result of transepithelial electrical coupling between these electrogenic fluxes. The H+ pump in MR cells generates a transepithelial current (serosa to apical) which acts as a physiological voltage-clamp to hyperpolarize the apical membrane of P cells. This hyperpolarization can facilitate passive Na+ entry across the apical membrane against a threefold chemical gradient. Since both JH and JNa are sensitive to membrane potential, inhibition or activation of one will produce similar effects on the transport of the other ion. For example, inhibition of JH by ethoxzolamide will reduce JNa. Conversely, blocking JNa with amiloride also inhibits JH. These effects can be avoided or reversed if variations in membrane potential are prevented by voltage-clamping the epithelium. A paradoxical activation of JNa is observed when JH is stimulated by an acid load (CO2), despite inhibition of Na+ channel activity by H+ in P cells.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Energization of sodium absorption by the H(+)-ATPase pump in mitochondria-rich cells of frog skin. 149 Dec 27

Ciliary body explants from 30 human eyes were maintained in organ culture up to 14 days. The age of the donors ranged from 45 to 85 years, the post mortem time from 4 to 22 hours. The ciliary epithelium as well as the underlying stroma were studied light- and electronmicroscopically before incubation and after 1, 3, 5, 7 and 14 days of culture. At the same time intervals, the localization of Na/K-ATPase and carbonic anhydrase (CA) were examined histochemically. If the cells were already damaged before incubation in medium (9 cases), they did not recover in culture. Best results were obtained after 3 to 5 days of culture with a survival rate of more than 90% after 3 days and more than 70% after 5 days, respectively. Both the nonpigmented (NPE) and the pigmented epithelium (PE) of the pars plicata in culture retained the morphological characteristics of epithelia involved in active secretion, namely elaborate infoldings of the cell membranes, numerous mitochondria in the cytoplasm and high activity of Na/K-ATPase and CA. In addition the adjacent capillaries were still fenestrated. After longer incubation times (7-14 days) the NPE and PE cells were filled with increasing amounts of lipid droplets and glycogen granules, indicating changes in metabolism.
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PMID:Human ciliary body in organ culture. 164 31

We examined immunohistochemically the localization of three transport enzymes (carbonic anhydrase, Ca-II; sodium-potassium-activated adenosine triphosphatase, NaK-ATPase; bicarbonate-chloride exchanger, band III) in the anterior segment of the human eye. In accord with earlier studies, NaK-ATPase was primarily found in the corneal endothelium, but also in the corneal basal epithelial cell membranes. In addition, immunoreactivity for NaK-ATPase was observed in the non-pigmented epithelium of the ciliary processes and between the two epithelial cell layers. Ca-II immunoreactivity was found in the corneal endothelium as well as in the non-pigmented epithelial layer of the ciliary processes. Interestingly, band III immunoreactivity was found in the corneal endothelium, as similar to Ca-II, but not in the ciliary processes. These results show that, similar to many other tissues, Ca-II and band III immunoreactivities colocalize in the same cytologic site in the human corneal endothelium. Immunocytochemical detection of these key transport enzymes not only gives their accurate and reliable anatomical distribution, but also provides information on the electrolyte transport at these sites.
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PMID:Immunocytochemical localization of carbonic anhydrase, NaK-ATPase and the bicarbonate chloride exchanger in the anterior segment of the human eye. 165 41

Fibrocytes in the lateral wall and limbus of the gerbil cochlea evidenced a capacity for ion transport activity by immunostaining for transport mediating enzymes including Na,K-ATPase, carbonic anhydrase (CA) and creatine kinase (CK). Fibrocytes of the spiral ligament unlike those in the suprastrial region and limbus decreased in abundance from base to apex. Spiral ligament fibrocytes at a given position along the cochlea varied in content of transport related enzymes, and on the basis of immunostaining, location and orientation, were classified into four types. Type I fibrocytes under the stria vascularis stained for CA isozymes II and III and CK isozyme BB. Type II fibrocytes under the outer sulcus and spiral prominence epithelium were found to contain only Na,K-ATPase. Type III fibrocytes lying adjacent to bone in the inferior region of the spiral ligament contained CA II and III and CK isozymes BB and MM. Type IV fibrocytes located more superficially in the inferior part of the spiral ligament stained variably for all the enzymes. Superficial fibrocytes in the suprastrial area disclosed Na,K-ATPase whereas the underlying fibrocytes stained for CA and CK. Limbal fibrocytes reacted with antisera to all the enzymes except CA III. Most fibrocytes in stromal plates beneath the vestibular system's neurosensory epithelium contained Na,K-ATPase and CA II but not CA III. These findings point to cooperativity in fluid and ion transport between epithelial cells and neighboring fibrocytes and demonstrate functional diversity of fibrocytes of the inner ear providing a basis for classifying those in the spiral ligament.
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PMID:Differentiation of inner ear fibrocytes according to their ion transport related activity. 166 6


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