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)

The effects of gentamicin and G418 on the cellular function of LLC-PK1 epithelial pig kidney cells were investigated. Exposing the cells for 2 days to these aminoglycoside antibiotics inhibited the increase in cell-associated apical membrane enzyme activity (alkaline phosphatase, aminopeptidase, and gamma-glutamyltransferase). Kinetic analysis revealed that the maximal activity of alkaline phosphatase was reduced by these aminoglycosides. Both aminoglycosides inhibited [3H]leucine incorporation into microsomes prepared from LLC-PK1 cells. The LLC-PK1 cells transfected with DNA encoding aminoglycoside 3'-phosphotransferase II, designated T2000B, were resistant to G418 as assessed by colony formation assay and the number of floating dead cells and by assay of apical enzyme activity. After a 4-hr exposure to G418, [3H]leucine incorporation in the host LLC-PK1 cells was inhibited, whereas that in T2000B cells was relatively unaffected. Gentamicin inhibited [3H]leucine incorporation similarly in both cells. The inhibition of protein synthesis by aminoglycosides occurred earlier than that of apical enzyme activity. These findings suggest that the inhibition of protein synthesis by aminoglycoside antibiotics is a possible cause of the reduction in cell viability as well as the apical enzymes in LLC-PK1 cells.
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PMID:Cellular toxicity of aminoglycoside antibiotics in G418-sensitive and -resistant LLC-PK1 cells. 805 26

Populations of the renal epithelial cell line, LLC-PK1, acquire many properties characteristic of the proximal tubular cell at confluence. At confluence cells both enter a nonproliferative state and develop extensive cell-cell contacts. To determine if one or both factors is responsible for acquisition of the differentiated phenotype, growth arrest was initiated in populations of varying densities by two procedures (serum deprivation and thymidine block) and expression of several differentiated properties (Na-hexose symport activity, gamma-glutamyl transpeptidase activity, alkaline phosphatase activity, and villin protein) was examined. Induction of growth arrest resulted in expression of all differentiated properties even in subconfluent populations. The level of expression in a population was proportional to cell density at the initiation of growth arrest; higher density was associated with increased expression. Evidence indicated the existence of some minimal density below which cells could not express detectable levels of differentiated properties in response to induction of growth arrest. The procedure used to initiate growth arrest did not affect this behavior, indicating that initiation of cell growth arrest rather than hormone deprivation was the inducing factor. These results indicate that both cell growth state and cell density independently modulate expression of differentiated properties by the LLC-PK1 cell. These results are incorporated into a model in which cells in the absence of "appropriate" cell-cell contact arrest at a differentiation-incompetent cell cycle point. In the presence of appropriate cell-cell contact (as yet undefined) cells arrest at a distinct differentiation-competent cell cycle point and initiate expression of the differentiated phenotype.
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PMID:Role of cell density/cell-cell contact, and growth state in expression of differentiated properties by the LLC-PK1 cell. 816 71

Confluent LLC-PK1 cell populations expressed progressively proximal tubule-specific properties, including gamma-glutamyl transpeptidase activity, sodium hexose symport activity, alkaline phosphatase activity, and villin protein. This was paralleled by an increase in villin protein manifested at the single cell level. Chronic treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA) inhibited expression of proximal tubule-specific properties at the levels of enzyme activity, protein content, and mRNA content. Inhibition occurred in all cells of the population. TPA treatment induced a decrease in total protein kinase C (PKC)-alpha protein content and a change in subcellular localization from predominantly soluble to predominantly particulate. PKC-epsilon protein content was unchanged by TPA treatment. PKC-epsilon was localized in both soluble and particulate fractions of control cells but was localized predominantly in particulate fractions after TPA treatment. PKC-delta was barely detectable in control cells, but content was markedly increased by TPA. These results suggest that TPA-induced inhibition of expression of proximal tubule-specific properties is mediated through modulation of content and/or subcellular localization of one or more PKC isozymes, likely PKC-alpha.
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PMID:Chronic TPA treatment inhibits expression of proximal tubule-specific properties by LLC-PK1 cells. 877 61

Na+ crosses the luminal membrane of the proximal tubule primarily via Na+/H+ exchange (NHE), and NHE activity is influenced by thyroid status. Pharmacological, immunological, and kinetic studies indicate multiple isoforms of NHE, and four full-length cDNAs have been cloned to date. The aims of this study were to determine which NHE mRNAs (NHE1, -2, -3, and -4) were expressed in the rat proximal tubule, the relative abundance of each in the renal cortex, and the effect of thyroid status on their expression. By blot hybridization of poly(A)+ RNA, all NHE isoform mRNAs were detected in the rat renal cortex; NHE1, -2, and -3 in the proximal tubule; and NHE1 and -3 in LLC-PK1 cells. NHE3 mRNA abundance was fourfold higher than the other three isoforms in renal cortex. The effect of thyroid status was assessed in renal cortex from euthyroid, hypothyroid, and hyperthyroid rats. Although none of the NHE mRNA levels was altered in the transition from euthyroid to hypothyroid states, both NHE2 and NHE3 mRNA levels increased 1.5-fold in the transition from hypo- to hyperthyroidism. NHE3 protein, measured by immunoblot with the use of an NHE3-specific antibody, was detected at 83-85 kDa in renal cortex and codistributed on sorbitol gradients with the brush-border marker alkaline phosphatase. No significant difference in NHE3 protein abundance was detected between hypothyroid and hyperthyroid rats. In conclusion, in the renal cortex, the NHE3 isoform predominates at the mRNA level, is expressed in apical membranes, and increases at the mRNA but not the protein levels in response to thyroid hormone treatment, suggesting parallel changes in synthesis and turnover of NHE3 by thyroid hormone.
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PMID:Renal Na+/H+ exchanger isoforms and their regulation by thyroid hormone. 877 23

The effects of 1 alpha,25-dihydroxyvitamin D3 (1,25 (OH)2D3) and human growth hormone (hGH) on the activity of alkaline phosphatase (ALP) were evaluated in pig kidney LLC-PK1 cultured cells. 1,25(OH)2D3 (10(-9)-10(-6) mol L-1) and hGH (10(-7) mol L-1) increased ALP activity in these cells while no hormonal effect was detected on two other enzyme activities: gamma-glutamyl transferase and acid phosphatase. ALP activity was maximally increased after 4.5-6 h incubation with both hormones. The hormonal induction of ALP activity was prevented by a pretreatment of cells with actinomycin D. Thus, 1,25 (OH)2D3 and may be hGH could stimulate ALP activity via a transcription of some gene.
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PMID:1 alpha,25-dihydroxyvitamin D3 stimulated alkaline phosphatase activity in cultured pig kidney epithelial LLC-PK1 cells. 887 54

Among kidney tubular epithelial cell types, proximal tubule cells are one of the major renal targets for xenobiotics. Several in vitro culture models have been proposed for use of proximal tubule cells for in vitro pharmacotoxicology studies. This paper reports a comparative study of the response to cephaloridine exposure of two established cell lines from pig (LLC-PK1) and rabbit (LLC-RK1) kidneys and primary cultures of rat and rabbit proximal tubule cells. These cultured cells were first compared for their levels of activity of alpha-methylglucopyranoside transport, alkaline phosphatase, succinate dehydrogenase, and NADPH cytochrome c reductase, their glutathione-dependent activity levels, and their adenylate cyclase response pattern to stimulation by PTH and AVP. The results presented show major phenotypic differences between these four cellular models. The differences observed in glutathione-dependent mechanism activities and regulation may in part be responsible for the variability of the responses of these four cellular models when exposed to cephaloridine.
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PMID:Comparative impact of cephaloridine on glutathione and related enzymes in LLC-PK1, LLC-RK1, and primary cultures of rat and rabbit proximal tubule cells. 903 21

Phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis added to a culture of LLC-PK1 cells inhibited cell growth by 40%. In contrast with normal cells, the cells cultured in the presence of PI-PLC showed needle-like appendages which seemed to have been formed due to portions of the cell remaining adhered to the culture dish as the cell shrank. When LLC-PK1 cells were treated with PI-PLC, significant amounts of alkaline phosphatase and alkaline phosphodiesterase I were released specifically from the apical surface of the LLC-PK1 cells. Furthermore, PI-PLC treatment caused a delay of enzyme production and dome formation. These data indicate that glycosyl-phosphatidylinositol (GPI)-anchored proteins on the surface of LLC-PK1 cells are important in cell growth and differentiation. Also, the combined use of LLC-PK1 cells and PI-PLC of B. thuringiensis is effective for investigating the function of GPI-anchor proteins.
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PMID:Growth inhibition, morphological change, and ectoenzyme release of LLC-PK1 cells by phosphatidylinositol-specific phospholipase C of Bacillus thuringiensis. 917 52

Monolayers of the porcine-derived renal epithelial cell line, LLC-PK1, were used to characterize the effects of heat stress on Na+-glucose cotransport. Transepithelial current dependent on 5 mM glucose (I(Glc)), phloridzin-sensitive current (I(phz)), and total transepithelial current (I(total)) were measured as indicators of Na+-glucose cotransport. Severe heat shock (SHS; 45 degrees C for 1 h, then 37 degrees C for measurements) decreased transepithelial electrical resistance (TER), I(Glc), I(phz), and I(total) 50-70%. Mild heat shock (MHS; 42 degrees C for 3 h, then 37 degrees C for 12 h) induced accumulation of 72-kDa heat shock protein (HSP-72), decreased damage to TER from SHS, and prevented damage to I(Glc), I(phz), and I(total). Kinetic analysis showed that SHS damaged and MHS protected total Na+-glucose transport capacity (Vmax of I(Glc)). MHS alone increased TER (50%), I(Glc) (20%), I(total) (20%), and Vmax of I(Glc) (25%). On enhancement of the Na+ gradient by depletion of intracellular Na+, MHS increased I(Glc) 50% and had no effect on transepithelial Na+-dependent sulfate reabsorptive flux measured concurrently or in Na+-replete tissues. These effects of MHS were not reflected in effects on cell survival or luminal membrane surface area as indicated by lactate dehydrogenase or alkaline phosphatase release. In conclusion, HSP-72-inducing heat treatment both protected and enhanced Na+-glucose cotransport independently of the luminal membrane Na+ gradient and selectively with respect to effects on TER, reabsorptive sulfate transport, cell survival, and luminal membrane surface area.
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PMID:Heat shock-induced protection and enhancement of Na+-glucose cotransport by LLC-PK1 monolayers. 936 30

Intracellular signal transduction for regulation of alkaline phosphatase (ALP) activity in renal epithelial cells treated with calcitonin is not yet completely understood, although it is known that calcitonin receptors couple to cyclic AMP-dependent protein kinase (PKA) and calcium/phospholipid-dependent protein kinase (PKC). Salmon calcitonin increased the cyclic AMP content in LLC-PK1 porcine kidney cells in a concentration-dependent manner. When the confluent cells were incubated for 47 h after a 1 h-pulse exposure or continuously exposed to calcitonin and forskolin for 48 h, ALP activity in the cells was increased by calcitonin about 2-fold compared with the basal activity at the maximum level but was not dependent on the exposure time; it was markedly increased by forskolin in parallel with the exposure time. The increase in activity produced by calcitonin was abolished by a PKA inhibitor H-89, and, in contrast, potentiated by a PKC inhibitor, NA-382 to near the forskolin-induced level. These results indicate that calcitonin exerts a dual-regulation of ALP activity in LLC-PK1 cells, positively through the PKA pathway and negatively through PKC.
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PMID:Dual regulation of alkaline phosphatase activity by calcitonin in porcine kidney cells. 944 8

To confirm the intracellular signal transduction in regulation of alkaline phosphatase (ALP) activity by calcitonin in kidney tubular cells, effects of several inhibitors of cyclic nucleotide phosphodiesterase (PDE) isoenzymes and cyclic AMP-dependent protein kinase (PKA) on the action of salmon calcitonin in porcine kidney tubular epithelial cells LLC-PK1 were examined. A confluent culture of LLC-PK1 cells was treated with calcitonin and inhibitors in Dulbecco's modified Eagle's medium supplemented with 0.1% bovine serum albumin, and intracellular cyclic AMP content and ALP activity were measured after incubation for 30 min and 48 hr, respectively. Calcitonin and PDE 4 inhibitors increased cyclic AMP level and ALP activity in the cells, and PDE 4 inhibitors synergistically potentiated the effects of calcitonin. Calcitonin induced ALP activation by treatment for the first 1 hr, as well as continuous treatment for 48 hr, while it never increased the enzyme activity just after 1-hr exposure. Rolipram, an inhibitor of PDE 4 isoenzyme, induced ALP activation by itself and in combination with calcitonin by only a long term treatment (48 hr). The activation of ALP by calcitonin and rolipram each alone and in combination was completely abolished by a PKA inhibitor, H-89. These results confirm that calcitonin induces ALP activation through the cyclic AMP-PKA pathway and that PDE 4 isoenzyme is closely associated with the calcitonin-receptor system and plays a major role in hydrolysis of cyclic AMP produced in the kidney tubular cells.
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PMID:Role of phosphodiesterase 4 isoenzyme in alkaline phosphatase activation by calcitonin in porcine kidney LLC-PK1 cells. 954 Dec 82


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