Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Ifosfamide (IF) is an alkylating cytostatic derived from nitrogen mustard. In addition to its well-known urotoxic effects (hemorrhagic cystitis), several cases of Fanconi syndrome following IF therapy have been reported. No information is available concerning the pathomechanisms of this tubulotoxicity. We used the permanent renal epithelial cell line LLC-PK1 in order to investigate whether major metabolites of IF (i.e. 4-OH-IF, acrolein and chloracetyldehyde) induced the transport defects most frequently detected after IF therapy in vivo. LLC-PK1 cells of passages 162-177, grown in plastic culture dishes, were used in a confluent state. Sodium-dependent and independent fluxes of l-[3H]alanine and of D-[3H]glucose were determined by standard techniques. Activities of marker enzymes of apical and basolateral membranes, of mitochondria and of endoplasmic reticulum were determined in cell homogenates. IF itself has no detectable effect on fluxes of l-alanine and D-glucose in LLC-PK1 cells. The IF metabolite 4-OOH-IF induces a clear inhibition of sodium-dependent fluxes of both substrates after a 24-hour exposure of cells to 100 mumol/l of 4-OOH-IF. Chloracetaldehyde induces a biphasic response of sodium-dependent fluxes of l-alanine with increased uptake rates at low concentrations (< 200 mumol/l) and with a short incubation time, while higher concentrations and long exposure of the cells leads to a reduction in sodium coupled transport. Glucose transport is affected in a comparable way, however, in contrast to alanine transport, chloracetaldehyde also stimulates sodium-independent fluxes of glucose. Acrolein is the most toxic substance tested. It severely damages cell monolayers at concentrations beyond 75 mumol/l. Sodium-coupled glucose and alanine transport is inhibited by acrolein at concentrations higher than 50 mumol/l. Sodium-coupled glucose transport is more sensitive to all metabolites tested than alanine transport. While acrolein strongly affects both transport systems, marker enzymes of the apical plasma membrane, i.e. alkaline phosphatase and leucine amino-peptidase, are not significantly inhibited, suggesting a specificity of the toxic effect for the transport proteins. We conclude that LLC-PK1 cells represent a good model for further investigation of the pathogenesis of Fanconi syndrome after IF therapy. Sodium-dependent transport systems are more sensitive to acrolein than other cell surface proteins.
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PMID:Inhibition of sodium-dependent transport systems in LLC-PK1 cells by metabolites of ifosfamide. 128 22

The mechanism of a gentamicin-induced decrease in apical membrane enzyme activities was investigated in LLC-PK1 cells. Increasing activities of apical membrane enzymes (alkaline phosphatase, aminopeptidase, and gamma-glutamyltransferase) were markedly suppressed by gentamicin during growth in culture. On the other hand, a lesser effect was observed when the activities of these enzymes were decreasing or relatively constant. Gentamicin treatment decreased the maximal enzyme activities of alkaline phosphatase and aminopeptidase, indicating that the number of active enzyme molecules in the apical membrane was decreased by gentamicin. [3H]Leucine incorporation in LLC-PK1 cells was inhibited by gentamicin in a dose-dependent manner, followed by a reduction of total protein. In addition, a well-known protein synthesis inhibitor, cycloheximide, also decreased the apical enzyme activities. These results suggest that the inhibition of protein synthesis by gentamicin is a possible cause of the decreased activities of apical membrane enzymes in LLC-PK1 cells. The inhibition of protein synthesis may be related to the nephrotoxicity induced by aminoglycoside antibiotics.
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PMID:Inhibition of apical membrane enzyme activities and protein synthesis by gentamicin in a kidney epithelial cell line LLC-PK1. 129 34

The established renal epithelial cell line LLC-PK1 retained in tissue culture several differentiated properties of renal proximal tubular cells. By adapting LLC-PK1 cells to glucose-free culture conditions, we recently succeeded in isolating a gluconeogenic strain of LLC-PK1 cells capable of growing in the absence of hexoses. In contrast to the parental wild type, the isolated strain expressed fructose-1,6-bisphosphatase activity and was, therefore, designated LLC-PK1-FBPase+. Besides the differences in glucose metabolism, the isolated gluconeogenic substrain differs form the parental wild type with respect to morphological appearance and the expression of apical membrane marker enzymes. LLC-PK1-FBPase+ cells display a drastic accumulation of autophagic vacuoles, disappearance of apical membrane alkaline phosphatase activity, and increased gamma-glutamyltranspeptidase activity. In order to find out whether or not a low alkaline phosphatase activity in combination with the enhanced formation of autophagic vacuoles is related to a change in apical membrane surface, we utilized a combined light and electron microscopic morphometric procedure to determine the absolute amount of organelle volumes and membrane surface areas. This stereologic approach shows that LLC-PK1-FBPase+ cells display a tenfold increase in the volume of autophagic vacuoles and the lysosomal compartment. Analysis of lysosomal enzyme activities, however, revealed no changes as compared to wild-type cells. The apical membrane surface of gluconeogenic cells was found to be increased by 80%. Karyotype analysis revealed that LLC-PK1 wild-type cells were diploid, whereas FBPase+ cells exhibited polyploidy with a high percentage of tetraploid nuclei. Culturing LLC-PK1-FBPase+ cells in the presence of 5 mM glucose does not abolish the morphological and biochemical changes described, indicating the stability of the FBPase+ strain.
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PMID:Morphological and biochemical changes of LLC-PK1 cells during adaptation to glucose-free culture conditions. 169 Sep 7

The Na(+)-dependent hexose carrier, an endogenous apical marker, develops during differentiation of LLC-PK1, an established cell line with characteristics of the proximal tubule. This development was inhibited by the microtubule-disrupting drugs, colchicine and nocodazole, while it was insensitive to lumicolchicine. This strongly suggests that microtubules are involved in the plasma membrane expression of the Na(+)-dependent hexose carrier. We also analyzed the increase in activity of endogenous apical and basolateral membrane proteins during the polarization process. The development of three apical (Na(+)-dependent hexose carrier, gamma-glutamyltransferase and alkaline phosphatase) and one basolateral membrane protein (Na+/K(+)-ATPase) was studied during the reorganization of LLC-PK1 cells into a polarized epithelium. Colchicine inhibited the rapid, transient increase in the expression of the Na(+)-dependent hexose carrier during this polarization process. A similar result was observed for the development of the other apical proteins, while the development of Na+/K(+)-ATPase seemed to be largely insensitive to colchicine. Our results are in agreement with the model that the vesicles containing the apical membrane proteins use microtubules as tracks to reach the plasma membrane. The transport of vesicles containing basolateral membrane proteins clearly occurs by a different pathway which is independent on an intact microtubular network. Since the inhibition by the microtubule-disrupting drugs was complete, it can be concluded that after disruption of microtubules, the apical vesicles do not use the basolateral pathway by default.
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PMID:Development of the Na(+)-dependent hexose carrier in LLC-PK1 cells is dependent on microtubules. 197 53

Freshly isolated rabbit proximal tubules (PT), confluent primary rabbit proximal tubule cultures (PTC) and LLC-PK1 cells were characterised. Brushborder enzyme activities were lower in PTC than in LLC-PK1: ratios were 0.026 for alkaline phosphatase (AP), 0.458 for alanine aminopeptidase (AAP) and 0.514 for gamma-glutamyl transpeptidase (GGT). PT/PTC ratios were 79.7 for AP, 7.96 for AAP and 3.45 for GGT. Specific activities of hexokinase (HK) and lactate dehydrogenase (LDH) were high in cultured cells as compared to PT: PT/PTC ratios were 0.063 and 0.033, while PTC/LLC-PK1 ratios were 0.406 and 1.19 for HK and LDH respectively. PTC/LLC-PK1 ratios were 2.21 for Na/K ATPase, 2.07 for succinate dehydrogenase, 1.12 for cathepsin B, 0.607 for N-acetyl-beta-D-glucosaminidase and 8.98 for glutathione-S-transferase. Adenylate cyclase response to parathormone (PTH), was similar in PTC and PT, but stimulated/basal ratios were higher in PT than in PTC. LLC-PK1 cells were stimulated by thyrocalcitonin (SCT), arginin-vasopressin (AVP) and PTH; stimulated/basal ratios ranked AVP greater than PTH greater than SCT. Differences between both types of cultures affect the choice of in vitro model for nephrotoxicity studies.
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PMID:Adenylate cyclase responses and biochemical characterization of primary rabbit proximal tubular cell cultures and LLC-PK1 cells. 228 70

The inhibitory action of orellanine (3,3',4,4'-tetrahydroxy-2,2'-dipyridyl-1,1'-dioxide), a fungal toxin of Cortinarius orellanus Fr. and C. orellanoides R. Hry., on alkaline phosphatase isoenzymes was studied. Orellanine specifically inhibited alkaline phosphatase activity in LLC-PK1 renal epithelial cell cultures and in the colon carcinoma cell line Caco-2 without affecting gamma-glutamyl transpeptidase activity. Kinetic studies revealed that orellanine acts on renal alkaline phosphatase as a noncompetitive inhibitor, whereas the intestinal and placental isoforms are inhibited competitively.
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PMID:Differential inhibitory action of the fungal toxin orellanine on alkaline phosphatase isoenzymes. 256 29

Three clones of the pig kidney cell line LLC-PK1 were isolated and characterized with regard to morphology, growth, proximal tubule enzyme activity, sugar uptake capacity, and hormone and drug responsiveness in a defined medium. Clone N4 was similar in morphology to the wild type (WT), whereas clone F8 showed loose attachment to the substrate, formed large, sweeping domes, and had an elongated desmosome junction between cells. The third clone, F2, did not form domes and showed a marked reduction in growth rate. Cultures of WT, N4, and F8 had higher specific activities of the enzyme alkaline phosphatase and gamma-glutamyl transpeptidase at confluence relative to growing cells; however, there was no evidence of an increase in activity of either enzyme at confluence in F2. Phlorizin-sensitive alpha-methyl-D-glucoside uptake and cytochalasin B-sensitive 2-deoxy-D-glucose uptake were measured in confluent cultures grown on porous filter supports. None of the clones lacked either of the hexose transport systems, although quantitative differences were evident. N4 cells grown in a defined medium in 96-well culture plates were tested in situ for their enzyme responses to differentiation inducers, tumor promoters, and hormones. Alkaline phosphatase activity was significantly increased at confluence by serum, parathyroid hormone (PTH), and vasopressin (AVP), and was decreased by tetradecanoylphorbol acetate (TPA) and epinephrine (EPI). Glutamyl transpeptidase activity was decreased at confluence by serum, TPA, and EPI. Similar tests on alpha-methyl-D-glucoside uptake showed that serum, TPA, PTH, and AVP had no significant effect on phlorizin-sensitive uptake; however, calcitonin increased uptake by 84% (n = 18). It was concluded that LLC-PK1 clones maintained in a defined medium are useful models for studying renal cell function.
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PMID:Growth, enzyme activity, sugar transport, and hormone supplement responses in cells cloned from a pig kidney cell line LLC-PK1. 256 38

Membrane glycoproteins and glycolipids play an important role in epithelial organization, transport and function. To study the effects of exogenous carbohydrates on the expression of glycoproteins, cells of the renal epithelial line LLC-PK1 were cultured on different nutritive carbohydrate sources and on uridine, which is, despite striking differences, known to substitute all essential nutritive functions of glucose. LLC-PK1 cultures were long-term adapted to growth in culture medium containing 0.5, 5, 10 and 25 mM glucose, and 5 mM fructose, galactose and uridine, respectively, as the sole carbohydrate source. These growth conditions elicited adaptive changes in the expression of enzyme activities of alkaline phosphatase and gamma-glutamyltranspeptidase, integral membrane glycoproteins exclusively localized in the apical membrane of LLC-PK1 cells. SDS-PAGE of membrane preparations of adapted LLC-PK1 cells revealed a strong induction of several protein bands between 13.5 and 47 kD in fructose-grown cells, while in plasma membranes of cells grown in galactose several protein bands between 62 and 70 kD decreased. Changes in the secretion pattern of proteins into the culture medium were most prominent in uridine-grown cells compared to controls grown on 25 mM glucose.
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PMID:Modification of membrane protein expression and protein secretion in LLC-PK1 cultures grown on different carbohydrates. 257 49

Sodium-dependent transport of phosphate was studied in LLC-PK1 cells that had been deprived of phosphate (Pi). Compared with control cells (fed with 2 mM Pi) a twofold increase in the rate of Na-Pi cotransport was observed in cells incubated for 15 h in a phosphate-free medium, whereas transport of L-alanine and the specific activity of alkaline phosphatase were not changed. The same adaptive response was observed with apical membrane vesicles isolated from Pi-deprived cells. In both experimental systems Pi deprivation caused a change in the Vmax but not in the apparent Km (for Pi) of the cotransport system. Adaptation of the Na-Pi cotransport was triggered by free phosphate concentrations between 0 and 100 microM. Over the first 20 h the adaptive response was found to be a linear process that could be prevented by 70 microM cycloheximide. Adapted cells that were re-treated with phosphate showed a rapid (less than 3 h) decrease in the Na-Pi transport. The data suggest that LLC-PK1 cells adapt to low Pi conditions by increasing the rate of the Na-Pi cotransport, which is located in the apical membrane. Two mechanisms may be involved in the adaptive response: a long-term process involving new protein synthesis, and a short-term response involving activation-inactivation of transport systems already existing.
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PMID:Adaptation of phosphate transport in phosphate-deprived LLC-PK1 cells. 397 Jan 60

The effects of aminoglycoside antibiotics on cellular functions of the LLC-PK1 kidney epithelial cell line were studied as a model system for aminoglycoside nephrotoxicity. The treatment with aminoglycoside antibiotics for 3 days caused a decrease in the dome number in the confluent LLC-PK1 cells and an increase in the floating cells in the culture medium. The inhibition of dome formation was dose-dependent and the rank-order of the degree of inhibition was compatible with the rank-order of in vivo nephrotoxicity. Aminoglycosides also decreased the intracellular content of cyclic AMP, with a correlation between the alteration of dome formation and cyclic AMP content. The specific activities of N-acetyl-beta-D-glucosaminidase (marker for lysosomes), aminopeptidase and alkaline phosphatase (marker for apical membranes) and (Na++K+)-adenosine triphosphatase (marker for basolateral membranes) in the homogenate were decreased by gentamicin treatment. Lysosomal and apical membrane enzymes released into the culture medium were increased by gentamicin treatment. The ultrastructural alterations in the lysosomes of gentamicin-treated cells also were observed. Above results suggest that aminoglycoside toxicity to LLC-PK1 cells may be similar to that reported for renal tubules.
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PMID:Effect of aminoglycoside antibiotics on cellular functions of kidney epithelial cell line (LLC-PK1): a model system for aminoglycoside nephrotoxicity. 608 64


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