Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.1.21 (CPT)
 4,580 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During development, the voltage dependence of single rat ventricular sodium channels shifts to more negative potentials. This shift is mimicked by coculture of neonatal myocytes with sympathetic neurons or by a 96-h exposure to 8-(4-chlorophenylthio) adenosine 3',5'-cyclic monophosphate (CPT-cAMP). The prolonged exposure to CPT-cAMP suggests that this is not a short-term modulatory effect on the sodium channel, but rather may reflect a trophic action. Here we examine the effect of CPT-cAMP using whole cell recording to investigate further the time period required for the effect. Sodium current was measured in a 50 mM NaCl bath solution at 20 +/- 1 degree C using the whole cell patch-clamp technique after exposure of myocytes to CPT-cAMP (0.25 mM) for 0,0.5,20, or 24 h. The relationship between the time constant of decay (tauh) of the sodium current and test voltage (V1) showed a shift to more hyperpolarizing voltages after exposure to CPT-cAMP for 24 h. In addition, the midpoint of the steady-state inactivation curve (V 1/2) was shifted from -75.8 +/- 1.1 mV (0-h exposure) to -83.3 +/- 1.6 mV (24-h exposure) (P < 0.05). Exposure for 0.5 h to CPT-cAMP did not alter the tauh or V 1/2 of the sodium current. However, exposure to CPT-cAMP for 20 h, followed by a 4-h washout period, produced an effect similar to that of the 24-h exposure. Thus the lack of effect of acute (0.5 h) exposure to CPT-cAMP and the persistence of the effect after washout of CPT-cAMP for 4 h suggest that adenosine 3',5'-cyclic monophosphate may play a trophic role in sodium channel development.
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PMID:An analogue of cAMP mimics developmental change in neonatal rat ventricular myocyte sodium current kinetics. 876 51

Liddle's disease is an autosomal dominant genetic disorder characterized by severe low renin hypertension ("pseudoaldosteronism") that has been genetically linked to a locus on chromosome 16 encoding the beta-subunit of an amiloride-sensitive Na+ channel (ASSC) (15). Peripheral blood lymphocytes (PBL) express ASSC that are functionally indistinguishable from those expressed by Na(+)-reabsorbing renal epithelial cells (3, 5). The amiloride-sensitive Na+ conductance in PBL from affected and unaffected individuals from the original Liddle's pedigree was examined using whole cell patch clamp. Typically, the basal Na+ currents in cells from affected individuals were maximally activated. Basal Na+ currents in cells from unaffected individuals were minimal and could be maximally activated by superfusion with 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (CPT-cAMP). Affected cells could not be further stimulated with CPT-cAMP. Superfusion with a supermaximal concentration of amiloride (2 microM) inhibited both the cAMP-activated Na+ conductance in unaffected cells and the constitutively activated inward conductance in affected cells. Cytosolic addition of a peptide identical to the terminal 10 amino acids of the truncated beta-subunit normalized the cAMP-mediated but not the pertussis toxin-induced regulation of the mutant ASSC. The findings show that lymphocyte ASSC are constitutively activated in affected individuals, that a mutation of the beta-subunit alters ASSC responsiveness to specific regulatory effectors, and that the cellular mechanism responsible for the pathophysiology of Liddle's disease is abnormal regulation of Na+ channel activity. These findings have important diagnostic and therapeutic implications and provide a cellular phenotype for the diagnosis of pseudoaldosteronism.
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PMID:Liddle's disease: abnormal regulation of amiloride-sensitive Na+ channels by beta-subunit mutation. 877 46

Effect of dietary fat type on beta-oxidation of brown adipose tissue and Na+ channel density of brain nerve membrane was studied in rats. Rats were fed an experimental diet containing lard, high oleic safflower oil, safflower oil or linseed oil for 12 weeks. The activities of carnitine palmitoyltransferase and cytochrome oxidase in brown adipose tissue were significantly lower in rats fed the lard diet than in those fed the high-oleic safflower oil diet, safflower oil diet or linseed oil diet. However, the peroxisomal beta-oxidation activity in brown adipose tissue was significantly higher in rats fed the lard diet than in those fed the other diet. The Na+ channel density in brain nerve membrane was not significantly different among the diet groups. These results suggest that intake of the lard diet rich in saturated fatty acids, compared with the vegetable oil diets rich in unsaturated fatty acids decrease mitochondrial beta-oxidation in brown adipose tissue, and that the dietary fat type has a differential effect on mitochondrial and peroxisomal beta-oxidation in brown adipose tissue.
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PMID:Effect of dietary fat type on beta-oxidation of brown adipose tissue and Na+ channel density of brain nerve membrane in rats. 878 Sep 74

1. In the present study we examined whether interleukin-1 beta (IL-1 beta) increases the activity of adenylyl cyclase in vascular smooth muscle cells and determined its role in the cytokine-induced expression of the inducible nitric oxide synthase (iNOS) and activation of nuclear transcription factor-kappa B (NF-kappa B). In addition the interaction between cyclic AMP- and cyclic GMP-elevating agonists on the IL-1 beta-stimulated expression of iNOS was examined. 2. Exposure of vascular smooth muscle cells to IL-1 beta stimulated the formation of cyclic AMP but not of cyclic GMP. The intracellular level of cyclic AMP reached a maximum within 1 h and then gradually declined over the next 5 h. This IL-1 beta (60 u ml-1)-stimulated formation of cyclic AMP was modest (about 3 fold at 60 u ml-1 for 1 h) compared to that evoked by isoprenaline (about 9 fold at 3 x 10(-6) M for 2 min). 3. The IL-1 beta (60 u ml-1 for 24 h)-stimulated accumulation of nitrite, which was taken as an index of NO production, was concentration-dependently increased by preferential inhibitors of cyclic AMP-dependent phosphodiesterases (rolipram and trequinsin). This effect was reproduced by a specific activator of the cyclic AMP-dependent protein kinase(s) A, Sp-8-CPT-cAMPS (10(-4) M) but was prevented by a specific inhibitor of cyclic AMP-dependent protein kinase(s) A, Rp-8-CPT-cAMPS (10(-4) M). These compounds alone [rolipram (10(-6) M), trequinsin (3 x 10(-6) M) and Sp-8-CPT-cAMPS (10(-4) M)] slightly but significantly increased the release of nitric oxide while Rp-8-CPT-cAMPS elicited no such effect. 4. Inducible NOS protein was expressed in IL-1 beta (30 u ml-1, 24 h)-stimulated smooth muscle cells as assessed by Western blot analysis. The level of iNOS protein was markedly increased in smooth muscle cells which had been exposed to IL-1 beta in combination with either rolipram (3 x 10(-6) M) or Sp-8-CPT-cAMPS (10(-4) M) but was reduced in those exposed to IL-1 beta and Rp-8-CPT-cAMPS (10(-4) M). A weak expression of iNOS protein was found in smooth muscle cells which had been exposed to either Sp-8-CPT-cAMPS or rolipram alone for 24 h while Rp-8-CPT-cAMPS elicited no such effect. 5. Exposure of smooth muscle cells to IL-1 beta (30 u ml-1) for 30 min increased the level of NF-kappa B-DNA complexes in nuclear extracts as detected by electrophoretic mobility shift assay. Similar levels of NF-kappa B-DNA complexes were found in cells which had been exposed to IL-1 beta in combination with either Sp-8-CPT-cAMPS (10(-4) M), trequinsin (10(-6) M) or rolipram (10(-6) M). None of the modulators alone affected the basal level of NF-kappa B binding activity. 6. NO-donors [sodium nitroprusside (SNP) 10(-4) M; dinitrosyl-iron-di-L-cysteine-complex (DNIC), 10(-4) M; 3-morpholino-sydnonimine (SIN-1), 10(-4) M] and atrial natriuretic factor (10(-6) M) significantly increased the IL-1 beta (30 or 60 u ml-1, 24 h)-stimulated expression of iNOS protein and activity as assessed indirectly by the conversion of oxyhaemoglobin to methaemoglobin. In the absence of IL-1 beta, SNP (10(-4) M, 24 h) but not the other cyclic GMP-dependent vasodilators caused a modest expression of iNOS protein. No such effect was found in smooth muscle cells exposed to SNP in combination with Rp-8-CPT-cAMPS (10(-4) M) while an increased level of iNOS protein was found in those exposed to SNP in combination with either Sp-8-CPT-cAMPS (10(-4) M) or rolipram (3 x 10(-6) M). 7. Exposure of vascular smooth muscle cells to either S-nitroso-L-cysteine (Cys-SNO, 10(-4) M), SNP (10(-4) M) or SIN-1 (10(-4) M) for 35 min affected minimally the basal activation of NF-kappa B but abolished that evoked by IL-1 beta (30 u ml-1 added during the last 30 min). However, addition of Cys-SNO following the stimulation with IL-1 beta (during the last 5 min of the 30 min exposure period) reduced the level of NF-kappa B-DNA complexes only slightly. 8. These data indicate that the cyclic AMP-dependent pathway plays a decisi
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PMID:Effect of cyclic GMP-dependent vasodilators on the expression of inducible nitric oxide synthase in vascular smooth muscle cells: role of cyclic AMP. 890 45

Dopamine receptors are present in the medullary thick ascending limb (mTAL) of Henle, but their effect on ion transport in this nephron segment has not been tested. Therefore, we studied the short-term effects of dopamine on Na(+)-K(+)-2Cl- cotransport (assessed by 100 microM bumetanide-sensitive 86Rb uptake) in rat mTAL tubular suspensions. Dopamine (1 microM) stimulated bumetanide-sensitive 86Rb uptake (72.1 +/- 10.6% vs. control, n = 5) by increasing total 86Rb uptake and by decreasing bumetanide-insensitive 86Rb uptake; this effect was concentration dependent. The dopamine-induced stimulation of Na(+)-K(+)-2Cl- cotransport activity was mimicked by calyculin A, a protein phosphatase (PP) inhibitor, and Sp isomer of adenosine 3',5'-cyclic monophosphothioate (Sp-cAMP[S]), a protein kinase A (PKA) agonist, and blocked by Rp isomer of 8-(4-chlorophenylthio)-cAMP[S] (Rp-8-CPT-cAMP[S]), a PKA inhibitor (n = 5). Dopamine did not increase the stimulatory effect of the PP inhibitor. However, the stimulatory effect of the PP inhibitor and PKA agonist was additive and approached the stimulatory effect of dopamine. The stimulatory effects of dopamine, PP inhibitor, and PKA agonist persisted even when intracellular sodium was clamped by 5 microM monensin. When K+ channels were blocked by 1 mM BaCl2, the effects of dopamine and calyculin A on the cotransport were no longer apparent, although the stimulatory effect of the PKA agonist was attenuated. We conclude that dopamine stimulates Na(+)-K(+)-2Cl- cotransport activity. This action is mediated mainly by PKA-dependent phosphorylation/dephosphorylation processes and modulated by dopamine actions on K+ channels.
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PMID:Stimulation of Na(+)-K(+)-2Cl- cotransport in rat medullary thick ascending limb by dopamine. 899 53

1. There is evidence that defective submucosal gland secretion contributes to the airway pathology of cystic fibrosis (CF). Using a capacitance probe technique, we have compared fluid transport across submucosal gland cultures from individuals with and without CF. 2. Under baseline conditions, approximately 60% of non-CF cultures secreted fluid; the rest absorbed. In secreting tissues, amiloride increased secretion, whereas in absorbing tissues it reduced or reversed absorption. 5-Nitro-2(3-phenylpropylamino)-benzoate (NPPB) a blocker of the CF transmembrane conductance regulator (CFTR), converted secretion to absorption. Thus, the direction and magnitude of baseline fluid movement depended on a balance between active absorption of Na+ and cAMP-dependent secretion of Cl-. 3. 8-(4-Chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (CPT-cAMP), methacholine and luminal uridine 5'-triphosphate (UTP) all induced or increased fluid secretion across non-CF cultures. Results with NPPB and with 4,4'-diisothiocyanatostilbene-2,2'-disulphonate (DIDS), a blocker of Ca(2+)-activated Cl- channels, suggested that fluid secretion induced by CPT-cAMP was mediated primarily by CFTR; UTP acted entirely via Ca(2+)-activated Cl- channels, and methacholine activated both pathways. 4. All CF cultures showed baseline fluid absorption, which was abolished by amiloride. 5. CF cultures showed a normal secretory response to UTP, a reduced response to methacholine, and no response to CPT-cAMP. 6. Thus, the absorptive processes of airway glands are retained in CF, but the cAMP-dependent secretory process is lost. This would markedly reduce the water content of gland secretions. The resulting change in viscosity would contribute to the accumulation of airway mucus which is characteristic of this disease.
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PMID:Fluid transport across cultures of human tracheal glands is altered in cystic fibrosis. 921 22

The regulation of the voltage-activated chloride current conductance (GCl) in toad skin was investigated by the use of the SH reagents N-ethylmaleimide (NEM) and p-chloro-mercuricbenzenesulfonic acid PCMBS. This anion pathway is controlled by a voltage-sensitive gating regulator. Mucosal application of NEM decreased the voltage-activation in a time and concentration dependent manner, half-maximal inhibition being exerted at a concentration of 30 microM within 20 min. At concentrations higher than 100 microM, the voltage-activated GCl was near-completely and irreversibly inhibited in less than 10 min. Resting, deactivated conductance was essentially unaffected. NEM had no effect on active sodium transport (measured as Isc) under conditions, which fully dissipated the voltage-activated GCl. After complete inhibition of the voltage-activated GCl with NEM, chloride conductance could still be stimulated by CPT-cAMP as in control tissues. Under these conditions, NEM at concentrations above 1 mm decreased GCl reversibly. Mucosal application of PCMBS at 500 microM inhibited the activated conductance by 35%, which was slightly reversible. Inhibition of voltage-activated GCl, which was observed after mucosal addition of the membrane-impermeable NEM analogue, eosin-5-maleimide, was completely reversible after washout. This suggests that the binding site for the maleimide is not accessible from the external face of the apical membrane. Brief application of NEM at lower concentrations (1-3 min, </= 100 microM) led to partial inhibition of GCl, followed by occasionally complete recovery upon washout of NEM. Recovery of voltage-activated GCl was progressively attenuated and eventually disappeared after subsequent brief applications of NEM. This could reflect recruitment of permeation/control sites from a finite pool. The data are discussed in the frame of a working model for the voltage-activated Cl--pathway, that contains two principle components, i.e., an anion-selective permeation path which is controlled by regulatory protein(s).
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PMID:Effects of NEM on voltage-activated chloride conductance in toad skin. 930 39

Chronic salt stress in ducklings (Anas platyrhynchos) resulted in a sustained accumulation of cyclic AMP in the secretory cells of the nasal salt glands. Adaptive increases in the activity of the Na+/K+-ATPase, measured as ATP hydrolysis rates in freshly isolated tissue, were observed after 12 h of salt stress. This change in enzyme activity was associated with increases in protein abundance in the - as well as in the ss-subunit of Na+/K+-ATPase and an increase in ss-subunit glycosylation. We investigated whether the increase in the cytosolic cyclic AMP concentration and the adaptive changes in Na+/K+-ATPase activity were causally related. Using an organotypic tissue culture system for salt gland slices from unstressed (naive) ducklings, we produced similar changes in Na+/K+-ATPase activity and subunit abundance by treating cultured tissue with drugs that elevate cytosolic cyclic AMP levels (forskolin, 8-CPT-cAMP) during a 15 h culture period. Protein synthesis assays using cultured tissue revealed that elevations in cytosolic cyclic AMP level mediate increases in Na+/K+-ATPase subunit abundance by slowing down the degradation of ATPase subunits. This increase in the amount of enzyme protein was associated with a significant increase in Na+/K+-ATPase activity in tissue homogenates. The time course of these changes in cyclic-AMP-treated cultured tissue resembled that observed in salt-stressed intact animals, indicating that the elevation in cyclic AMP level in salt gland tissue may constitute a portion of the signalling events ultimately leading to the adaptive increase in Na+/K+-ATPase activity in vivo.
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PMID:Changes in Na+/K+-ATPase expression during adaptive cell differentiation in avian nasal salt gland 931 5

1. The objective of this study was to investigate the mechanism of PGE2 regulation of Cl- transport across glandular endometrial cells grown in primary culture. 2. Most of the basal short circuit current (Isc) was inhibited by luminal addition of 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) or glibenclamide, suggesting the presence of a basally active Cl- conductance in the apical membrane. 3. Basolateral addition of 10 microM PGE2 increased Isc by 41 +/- 3 microA. A similar response was observed when cells were treated with 8-(4-chlorophenylthio) adenosine 3',5'-cyclic monophosphate (CPT-cAMP). Pretreatment of monolayers with NPPB and glibenclamide blocked the PGE2 and cAMP-mediated increase in Isc, suggesting that the effects of PGE2 and cAMP were dependent on the activity of an apical NPPB- and glibenclamide-sensitive conductance. 4. Addition of 50 nM antiPGE2 antibody to the basolateral bathing solution decreased basal Isc by 20 % and shifted the threshold response to exogenous PGE2. This result suggests autocrine regulation of electrogenic Cl- transport by PGE2. 5. Experiments with amphotericin B-permeabilized monolayers revealed that the apical PGE2-activated, NPPB- and glibenclamide-sensitive conductance was Cl- dependent and that the current-voltage relationship and anion permeation properties (SCN->Br- > Cl- > I-) were characteristic of the cystic fibrosis transmembrane conductance regulator (CFTR). 6. Cultured porcine endometrial epithelial cells were specifically labelled with an antibody to a peptide sequence within the regulatory domain of CFTR. 7. The effect of PGE2 was blocked by basolateral addition of bumetanide and furosemide at concentrations that are selective for inhibition of Na+-K+-2Cl-cotransport activity. The effect of bumetanide on Isc was Cl- dependent, suggesting a role for the bumetanide-sensitive transport pathway in Cl- secretion. 8. PGE2 and cAMP also activated an outwardly rectifying basolateral K+ channel which presumably sustains the driving force for electrogenic Cl- efflux across the apical membrane. 9. The concentration-conductance and concentration-Isc response relationships for PGE2 showed that basolateral K+ permeability was rate limiting with respect to transepithelial anion secretion and that activation of a basolateral K+ channel by PGE2 was necessary to achieve maximum rates of Cl- secretion.
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PMID:Regulation of chloride secretion across porcine endometrial epithelial cells by prostaglandin E2. 949 Aug 13

This study aimed to characterize the cellular pathways along which nitric oxide (NO) influences the secretion of renin from the kidney. Using the isolated perfused rat kidney model, we found that the NO donor sodium nitroprusside (SNP) (1-30 mumol/l) induced a prompt, concentration-dependent fourfold increase of basal renin secretion. The membrane-permeable cGMP analogs 8-bromo-cGMP and 8-(4-chlorophenylthio)-cGMP (8-pCPT-cGMP; each 5-50 mumol/l) inhibited basal renin secretion and attenuated the stimulation of renin secretion by SNP. Conversely, the renin stimulatory effect of SNP was enhanced in the presence of the G kinase inhibitor Rp-8-CPT-cGMPS (10 mumol/l). The renin stimulatory effect of SNP was amplified in nominally calcium-free perfusate and was abolished in the presence of angiotensin II (1 nmol/l). Renin secretion stimulated by SNP was clearly attenuated by the A kinase inhibitor Rp-8-CPT-cAMPS (25 mumol/l). These findings indicate that the renin stimulatory effect of NO donors in renal juxtaglomerular cells cannot be explained by activation of G kinase and is also less likely to be causally related to the regulation of renin secretion by calcium. Because A kinase activity is required for the stimulation of renin secretion by SNP, it appears as if the renin stimulatory effect is causally related to the cAMP pathway controlling renin secretion.
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PMID:Stimulation of renin secretion by NO donors is related to the cAMP pathway. 957 95


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