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1.
Voltage-dependent stimulation of the Na(+)-K(+) pump by insulin in rabbit cardiac myocytes 总被引:4,自引:0,他引:4
Hansen PS Buhagiar KA Gray DF Rasmussen HH 《American journal of physiology. Cell physiology》2000,278(3):C546-C553
Insulin enhancesNa+-K+ pump activity in various noncardiactissues. We examined whether insulin exposure in vitro regulates Na+-K+ pump function in rabbit ventricularmyocytes. Pump current (Ip) was measured using thewhole-cell patch-clamp technique at test potentials(Vms) from 100 to +60 mV. When theNa+ concentration in the patch pipette([Na]pip) was 10 mM, insulin caused aVm-dependent increase in Ip.The increase was ~70% when Vm was at nearphysiological diastolic potentials. This effect persisted afterelimination of extracellular voltage-dependent steps and whenK+ and K+-congeners were excluded from thepatch pipettes. When [Na]pip was 80 mM, causingnear-maximal pump stimulation, insulin had no effect, suggesting thatit did not cause an increase in membrane pump density. Effects oftyrphostin A25, wortmannin, okadaic acid, or bisindolylmaleimide I inpipette solutions suggested that the insulin-induced increase inIp involved activation of tyrosine kinase,phosphatidylinositol 3-kinase, and protein phosphatase 1, whereasprotein phosphatase 2A and protein kinase C were not involved. 相似文献
2.
Buhagiar Kerrie A.; Hansen Peter S.; Gray David F.; Mihailidou Anastasia S.; Rasmussen Helge H. 《American journal of physiology. Cell physiology》1999,277(3):C461
Treatment of rabbits with angiotensin-converting enzyme (ACE)inhibitors increases the apparent affinity of theNa+-K+pump for Na+. To explore themechanism, we voltage clamped myocytes from control rabbits and rabbitstreated with captopril with patch pipettes containing 10 mMNa+. When pipette solutions wereK+ free, pump current(Ip) formyocytes from captopril-treated rabbits was nearly identical to thatfor myocytes from controls. However, treatment caused a significantincrease in Ipmeasured with pipettes containingK+. A similar difference wasobserved when myocytes from rabbits treated with the ANG II receptorantagonist losartan and myocytes from controls were compared.Treatment-induced differences in Ip wereeliminated by in vitro exposure to ANG II or phorbol 12-myristate 13-acetate or inclusion of the protein kinase C fragment composed ofamino acids 530-558 in pipette solutions. Treatmentwith captopril had no effect on the voltage dependence ofIp. We concludethat ANG II regulates the pump's selectivity for intracellularNa+ at sites near the cytoplasmicsurface. Protein kinase C is implicated in the messenger cascade. 相似文献
3.
Hansen PS Clarke RJ Buhagiar KA Hamilton E Garcia A White C Rasmussen HH 《American journal of physiology. Cell physiology》2007,292(3):C1070-C1077
The effect of diabetes on sarcolemmal Na+-K+ pump function is important for our understanding of heart disease associated with diabetes and design of its treatment. We induced diabetes characterized by hyperglycemia but no other major metabolic disturbances in rabbits. Ventricular myocytes isolated from diabetic rabbits and controls were voltage clamped and internally perfused with the whole cell patch-clamp technique. Electrogenic Na+-K+ pump current (Ip, arising from the 3:2 Na+-to-K+ exchange ratio) was identified as the shift in holding current induced by Na+-K+ pump blockade with 100 µmol/l ouabain in most experiments. There was no effect of diabetes on Ip recorded when myocytes were perfused with pipette solutions containing 80 mmol/l Na+ to nearly saturate intracellular Na+-K+ pump sites. However, diabetes was associated with a significant decrease in Ip measured when pipette solutions contained 10 mmol/l Na+. The decrease was independent of membrane voltage but dependent on the intracellular concentration of K+. There was no effect of diabetes on the sensitivity of Ip to extracellular K+. Pump inhibition was abolished by restoration of euglycemia or by in vivo angiotensin II receptor blockade with losartan. We conclude that diabetes induces sarcolemmal Na+-K+ pump inhibition that can be reversed with pharmacological intervention. sodium transport; insulin; angiotensin II; cardiomyopathy; hyperglycemia 相似文献
4.
Dietary cholesterol alters Na+/K+ selectivity at intracellular Na+/K+ pump sites in cardiac myocytes 总被引:1,自引:0,他引:1
Buhagiar KA Hansen PS Kong BY Clarke RJ Fernandes C Rasmussen HH 《American journal of physiology. Cell physiology》2004,286(2):C398-C405
A modest diet-induced increase in serum cholesterol in rabbits increases the sensitivity of the sarcolemmal Na+/K+ pump to intracellular Na+, whereas a large increase in cholesterol levels decreases the sensitivity to Na+. To examine the mechanisms, we isolated cardiac myocytes from controls and from rabbits with diet-induced increases in serum cholesterol. The myocytes were voltage clamped with the use of patch pipettes that contained osmotically balanced solutions with Na+ in a concentration of 10 mM and K+ in concentrations ([K+]pip) ranging from 0 to 140 mM. There was no effect of dietary cholesterol on electrogenic Na+/K+ current (Ip) when pipette solutions were K+ free. A modest increase in serum cholesterol caused a [K+]pip-dependent increase in Ip, whereas a large increase caused a [K+]pip-dependent decrease in Ip. Modeling suggested that pump stimulation with a modest increase in serum cholesterol can be explained by a decrease in the microscopic association constant KK describing the backward reaction E1 + 2K+ E2(K+)2, whereas pump inhibition with a large increase in serum cholesterol can be explained by an increase in KK. Because hypercholesterolemia upregulates angiotensin II receptors and because angiotensin II regulates the Na+/K+ pump in cardiac myocytes in a [K+]pip-dependent manner, we blocked angiotensin synthesis or angiotensin II receptors in vivo in cholesterol-fed rabbits. This abolished cholesterol-induced pump inhibition. Because the -isoform of protein kinase C (PKC) mediates effects of angiotensin II on the pump, we included specific PKC-blocking peptide in patch pipette filling solutions. The peptide reversed cholesterol-induced pump inhibition. partial reactions; protein kinase C; angiotensin converting enzyme inhibitors; arteriosclerosis; insulin resistance 相似文献
5.
K+ channels participate in the regulatory volume decrease (RVD) accompanying hepatocellular nutrient uptake and bile formation. We recently identified KCNQ1 as a molecular candidate for a significant fraction of the hepatocellular swelling-activated K+ current (IKVol). We have shown that the KCNQ1 inhibitor chromanol 293B significantly inhibited RVD-associated K+ flux in isolated perfused rat liver and used patch-clamp techniques to define the signaling pathway linking swelling to IKVol activation. Patch-electrode dialysis of hepatocytes with solutions that maintain or increase phosphatidylinositol 4,5-bisphosphate (PIP2) increased IKVol, whereas conditions that decrease cellular PIP2 decreased IKVol. GTP and AlF4 stimulated IKVol development, suggesting a role for G proteins and phospholipase C (PLC). Supporting this, the PLC blocker U-73122 decreased IKVol and inhibited the stimulatory response to PIP2 or GTP. Protein kinase C (PKC) is involved, because K+ current was enhanced by 1-oleoyl-2-acetyl-sn-glycerol and inhibited after chronic PKC stimulation with phorbol 12-myristate 13-acetate (PMA) or the PKC inhibitor GF 109203X. Both IKVol and the accompanying membrane capacitance increase were blocked by cytochalasin D or GF 109203X. Acute PMA did not eliminate the cytochalasin D inhibition, suggesting that PKC-mediated IKVol activation involves the cytoskeleton. Under isotonic conditions, a slowly developing K+ current similar to IKVol was activated by PIP2, lipid phosphatase inhibitors to counter PIP2 depletion, a PLC-coupled 1-adrenoceptor agonist, or PKC activators and was depressed by PKC inhibition, suggesting that hypotonicity is one of a set of stimuli that can activate IKVol through a PIP2/PKC-dependent pathway. The results indicate that PIP2 indirectly activates hepatocellular KCNQ1-like channels via cytoskeletal rearrangement involving PKC activation. KCNQ1; patch clamp; phosphatidylinositol 4,5-bisphosphate; regulatory volume decrease 相似文献
6.
Na+ influx and Na+-K+ pump activation during short-term exposure of cardiac myocytes to aldosterone 总被引:1,自引:0,他引:1
Mihailidou Anastasia S.; Buhagiar Kerrie A.; Rasmussen Helge H. 《American journal of physiology. Cell physiology》1998,274(1):C175
To examine the effect of aldosterone on sarcolemmalNa+ transport, we measuredouabain-sensitive electrogenicNa+-K+pump current(Ip) involtage-clamped ventricular myocytes and intracellularNa+ activity(aiNa) in right ventricularpapillary muscles. Aldosterone (10 nM) induced an increase in bothIp and the rateof rise of aiNa duringNa+-K+pump blockade with the fast-acting cardiac steroid dihydroouabain. Thealdosterone-induced increase inIp and rate ofrise of aiNa was eliminated bybumetanide, suggesting that aldosterone activates Na+ influx through theNa+-K+-2Clcotransporter. To obtain independent support for this, theNa+,K+, andCl concentrations in thesuperfusate and solution of pipettes used to voltage clamp myocyteswere set at levels designed to abolish the inward electrochemicaldriving force for theNa+-K+-2Clcotransporter. This eliminated the aldosterone-induced increase inIp. We concludethat in vitro exposure of cardiac myocytes to aldosterone activates theNa+-K+-2Clcotransporter to enhance Na+influx and stimulate theNa+-K+pump. 相似文献
7.
Ding Y Schwartz D Posner P Zhong J 《American journal of physiology. Cell physiology》2004,287(2):C413-C421
It has been suggested that L-type Ca2+ channels play an important role in cell swelling-induced vasoconstriction. However, there is no direct evidence that Ca2+ channels in vascular smooth muscle are modulated by cell swelling. We tested the hypothesis that L-type Ca2+ channels in rabbit portal vein myocytes are modulated by hypotonic cell swelling via protein kinase activation. Ba2+ currents (IBa) through L-type Ca2+ channels were recorded in smooth muscle cells freshly isolated from rabbit portal vein with the conventional whole cell patch-clamp technique. Superfusion of cells with hypotonic solution reversibly enhanced Ca2+ channel activity but did not alter the voltage-dependent characteristics of Ca2+ channels. Bath application of selective inhibitors of protein kinase C (PKC), Ro-318425 or Go-6983, prevented IBa enhancement by hypotonic swelling, whereas the specific protein kinase A (PKA) inhibitor KT-5720 had no effect. Bath application of phorbol 12,13-dibutyrate (PDBu) significantly increased IBa under isotonic conditions and prevented current stimulation by hypotonic swelling. However, PDBu did not have any effect on IBa when cells were first exposed to hypotonic solution. Furthermore, downregulation of endogenous PKC by overnight treatment of cells with PDBu prevented current enhancement by hypotonic swelling. These data suggest that hypotonic cell swelling can enhance Ca2+ channel activity in rabbit portal vein smooth muscle cells through activation of PKC. cell swelling; protein kinases; calcium current 相似文献
8.
Dependence of Na+-K+ pump current-voltage relationship on intracellular Na+, K+, and Cs+ in rabbit cardiac myocytes 总被引:2,自引:0,他引:2
Hansen PS Buhagiar KA Kong BY Clarke RJ Gray DF Rasmussen HH 《American journal of physiology. Cell physiology》2002,283(5):C1511-C1521
To examine effects of cytosolicNa+, K+, and Cs+ on the voltagedependence of the Na+-K+ pump, we measuredNa+-K+ pump current (Ip)of ventricular myocytes voltage-clamped at potentials(Vm) from 100 to +60 mV. Superfusates weredesigned to eliminate voltage dependence at extracellular pump sites.The cytosolic compartment of myocytes was perfused with patch pipette solutions with a Na+ concentration ([Na]pip)of 80 mM and a K+ concentration from 0 to 80 mM or withsolutions containing Na+ in concentrations from 0.1 to 100 mM and K+ in a concentration of either 0 or 80 mM. When[Na]pip was 80 mM, K+ in pipette solutionshad a voltage-dependent inhibitory effect on Ipand induced a negative slope of theIp-Vm relationship. Cs+ in pipette solutions had an effect onIp qualitatively similar to that ofK+. Increases in Ip with increasesin [Na]pip were voltage dependent. The dielectriccoefficient derived from[Na]pip-Ip relationships at thedifferent test potentials was 0.15 when pipette solutions included 80 mM K+ and 0.06 when pipette solutions were K+ free. 相似文献
9.
Buhagiar Kerrie A.; Hansen Peter S.; Bewick Nerida L.; Rasmussen Helge H. 《American journal of physiology. Cell physiology》2001,281(3):C1059
A reduction in angiotensinII (ANG II) in vivo by treatment of rabbits with theangiotensin-converting enzyme inhibitor, captopril, increasesNa+-K+ pump current (Ip)of cardiac myocytes. This increase is abolished by exposure of myocytesto ANG II in vitro. Because ANG II induces translocation of the-isoform of protein kinase C (PKC), we examined whether thisisozyme regulates the pump. We treated rabbits with captopril, isolatedmyocytes, and measured Ip of myocytes voltageclamped with wide-tipped patch pipettes. Ip ofmyocytes from captopril-treated rabbits was larger thanIp of myocytes from controls. ANG II superfusionof myocytes from captopril-treated rabbits decreasedIp to levels similar to controls. Inclusion ofPKC-specific blocking peptide in pipette solutions used to perfusethe intracellular compartment abolished the effect of ANG II. Inclusionof RACK, a PKC-specific activating peptide, in pipettesolutions had an effect on Ip that was similarto that of ANG II. There was no additive effect of ANG II andRACK. We conclude that PKC regulates the sarcolemmalNa+-K+ pump. 相似文献
10.
Internodal cells of Nitellopsis were made tonoplast-free byperfusion with a medium containing EGTA. Cytoplasmic concentrationsof solutes were controlled by a second perfusion with mediaof known composition. The electrogenic pump current (Ip), whichwas calculated from electrical data obtained from cells withand without ATP, was compared with the current carried by H+(IH+) across the plasma membrane. A close correlation betweenIp and IH+ was found under various internal and external conditions.(1) Ip and IH+ depended on the internal ATP and showed Michaelis-Mententype saturation curves. For Ip, Km was 120 µM and themaximum current Vmax was 15.1 mA m2, while for IH+, Kmwas 160 µM and Vmax was 16.6 mA m2. (2) Ip andIH+ showed almost the same IH2+ dependence. The Mg2+-dependentIp was 19.5 mA m2, while the Mg2+-dependent IH2+ was17.7 mA m2. (3) IH2+ was maximal at an external pH of8 and decreased both in acidic and alkaline pH ranges. Ip wasnearly equal to IH+ in the pH range between 8 and 5. (4) IH+became maximal at an internal pH of 7.3, which is nearly thesame as the pH for maximal electrogenecity found by Mimura andTazawa (1984). All these facts support the idea proposed in our previous paper(Takeshige et al. 1985) that the electrogenic ion pump locatedin the plasma membrane of Nitellopsis is the H+ pump.
1 Dedicated to Professor Dr. Erwin Bünning on the occasionof his 80th birthday. (Received June 21, 1985; Accepted December 20, 1985) 相似文献
11.
Brette F Lacampagne A Sallé L Findlay I Le Guennec JY 《American journal of physiology. Cell physiology》2003,285(2):C310-C318
Inactivation of the L-type Ca2+ current (ICaL) was studied in isolated guinea pig ventricular myocytes with different ionic solutions. Under basal conditions, ICaL of 82% of cells infused with Cs+-based intracellular solutions showed enhanced amplitude with multiphasic decay and diastolic depolarization-induced facilitation. The characteristics of ICaL in this population of cells were not due to contamination by other currents or an artifact. These phenomena were reduced by ryanodine, caffeine, cyclopiazonic acid, the protein kinase A inhibitor H-89, and the cAMP-dependent protein kinase inhibitor. Forskolin and isoproterenol increased ICaL by only 60% in these cells. Cells infused with either N-methyl-D-glucamine or K+-based intracellular solutions did not show multiphasic decay or facilitation under basal conditions. Isoproterenol increased ICaL by 200% in these cells. In conclusion, we show that multiphasic inactivation of ICaL is due to Ca2+-dependent inactivation that is reversible on a time scale of tens of milliseconds. Cs+ seems to activate the cAMP-dependent protein kinase pathway when used as a substitute for K+ in the pipette solution. L-type calcium current; calcium-dependent inactivation; facilitation; phosphorylation; cesium 相似文献
12.
Apoptosis repressor with caspase domain inhibits cardiomyocyte apoptosis by reducing K+ currents 总被引:8,自引:0,他引:8
Ekhterae D Platoshyn O Zhang S Remillard CV Yuan JX 《American journal of physiology. Cell physiology》2003,284(6):C1405-C1410
Cell shrinkageis an early prerequisite in programmed cell death, and cytoplasmicK+ is a dominant cation that controls intracellular ionhomeostasis and cell volume. Blockade of K+ channelsinhibits apoptotic cell shrinkage and attenuates apoptosis. We examined whether apoptotic repressor with caspase recruitment domain (ARC), an antiapoptotic protein, inhibits cardiomyocyte apoptosis by reducing K+ efflux throughvoltage-gated K+ (Kv) channels. In heart-derived H9c2cells, whole cell Kv currents (IK(V)) wereisolated by using Ca2+-free extracellular (bath) solutionand including 5 mM ATP and 10 mM EGTA in the intracellular (pipette)solution. Extracellular application of 5 mM 4-aminopyridine (4-AP), ablocker of Kv channels, reversibly reduced IK(V)by 50-60% in H9c2 cells. The remaining currents during 4-APtreatment may be generated by K+ efflux through4-AP-insensitive K+ channels. Overexpression of ARC inheart-derived H9c2 cells significantly decreasedIK(V), whereas treatment with staurosporine, apotent apoptosis inducer, enhanced IK(V)in wild-type cells. The staurosporine-induced increase inIK(V) was significantly suppressed and thestaurosporine-mediated apoptosis was markedly inhibited incells overexpressing ARC compared with cells transfected with thecontrol neomycin vector. These results suggest that theantiapoptotic effect of ARC is, in part, due to inhibition of Kvchannels in cardiomyocytes. 相似文献
13.
The effects ofcyanide (CN) on whole cell current measured with the perforated-patchmethod were studied in adrenal medullary cells. Application of CNproduced initially inward and then outward currents at 52 mV ormore negative. As the membrane potential was hyperpolarized, amplitudeand latency of the outward current (Io) by CNbecame small and long, respectively. A decrease in the externalNa+ concentration did not affectthe latency for CN-inducedIo but enhancedthe amplitude markedly. The CNIo reversedpolarity at 85 mV, close to the Nernst potential forK+, and was suppressed by theK+ channel blockers curare andapamin but not by glibenclamide, suggesting thatIo is due to theactivation of Ca2+-dependentK+ channels. Consistent with thisnotion, the Ca2+-mobilizingagents, muscarine and caffeine, also producedIo. Exposure toCN in a Ca2+-deficient medium for4 min abolished caffeine- or muscarine-induced Io withoutdevelopment ofIo, and additionof Ca2+ to the CN-containingsolution inducedIo. We concludethat exposure to CN producesCa2+-dependentK+ currents in an externalCa2+-dependent manner, probablyvia facilitation of Ca2+ influx. 相似文献
14.
Mechanotransduction by integrin is essential for IL-6 secretion from endothelial cells in response to uniaxial continuous stretch 总被引:3,自引:0,他引:3
Sasamoto A Nagino M Kobayashi S Naruse K Nimura Y Sokabe M 《American journal of physiology. Cell physiology》2005,288(5):C1012-C1022
We previously reported that uniaxial continuous stretch in human umbilical vein endothelial cells (HUVECs) induced interleukin-6 (IL-6) secretion via IB kinase (IKK)/nuclear factor-B (NF-B) activation. The aim of the present study was to clarify the upstream signaling mechanism responsible for this phenomenon. Stretch-induced IKK activation and IL-6 secretion were inhibited by application of 51 integrin-inhibitory peptide (GRGDNP), phosphatidylinositol 3-kinase inhibitor (LY-294002), phospholipase C- inhibitor (U-73122), or protein kinase C inhibitor (H7). Although depletion of intra- or extracellular Ca2+ pool using thapsigargin (TG) or EGTA, respectively, showed little effect, a TG-EGTA mixture significantly inhibited stretch-induced IKK activation and IL-6 secretion. An increase in the intracellular Ca2+ concentration ([Ca2+]i) upon continuous stretch was observed even in the presence of TG, EGTA, or GRGDNP, but not in a solution containing the TG-EGTA mixture, indicating that both integrin activation and [Ca2+]i rise are crucial factors for stretch-induced IKK activation and after IL-6 secretion in HUVECs. Furthermore, while PKC activity was inhibited by the TG-EGTA mixture, GRGDNP, LY-294002, or U-73122, PLC- activity was retarded by GRGDNP or LY-294002. These results indicate that continuous stretch-induced IL-6 secretion in HUVECs depends on outside-in signaling via integrins followed by a PI3-K-PLC--PKC-IKK-NF-B signaling cascade. Another crucial factor, [Ca2+]i increase, may at least be required to activate PKC needed for NF-B activation. nuclear factor-B; phosphatidylinositol 3-kinase; phospholipase C-; protein kinase C; intracellular Ca2+ concentration 相似文献
15.
Balut C Steels P Radu M Ameloot M Driessche WV Jans D 《American journal of physiology. Cell physiology》2006,290(1):C87-C94
In this study, we have investigated the dependence of Na+ transport regulation on membrane cholesterol content in A6 renal epithelia. We continuously monitored short-circuit current (Isc), transepithelial conductance (GT), and transepithelial capacitance (CT) to evaluate the effects of cholesterol extraction from the apical and basolateral membranes in steady-state conditions and during activation with hyposmotic shock, oxytocin, and adenosine. Cholesterol extraction was achieved by perfusing the epithelia with methyl--cyclodextrin (mCD) for 1 h. In steady-state conditions, apical membrane cholesterol extraction did not significantly affect the electrophysiological parameters; in contrast, marked reductions were observed during basolateral mCD treatment. However, apical mCD application hampered the responses of Isc and GT to hypotonicity, oxytocin, and adenosine. Analysis of the blocker-induced fluctuation in Isc demonstrated that apical mCD treatment decreased the epithelial Na+ channel (ENaC) open probability (Po) in the steady state as well as after activation of Na+ transport by adenosine, whereas the density of conducting channels was not significantly changed as confirmed by CT measurements. Na+ transport activation by hypotonicity was abolished during basolateral mCD treatment as a result of reduced Na+/K+ pump activity. On the basis of the findings in this study, we conclude that basolateral membrane cholesterol extraction reduces Na+/K+ pump activity, whereas the reduced cholesterol content of the apical membranes affects the activation of Na+ transport by reducing ENaC Po. epithelial Na+ channel; Na+-K+-ATPase activity; short-circuit current; methyl--cyclodextrin; channel open probability 相似文献
16.
Michailova A Lorentz W McCulloch A 《American journal of physiology. Cell physiology》2007,293(2):C542-C557
To investigate the mechanisms regulating excitation-metabolic coupling in rabbit epicardial, midmyocardial, and endocardial ventricular myocytes we extended the LabHEART model (Puglisi JL and Bers DM. Am J Physiol Cell Physiol 281: C2049–C2060, 2001). We incorporated equations for Ca2+ and Mg2+ buffering by ATP and ADP, equations for nucleotide regulation of ATP-sensitive K+ channel and L-type Ca2+ channel, Na+-K+-ATPase, and sarcolemmal and sarcoplasmic Ca2+-ATPases, and equations describing the basic pathways (creatine and adenylate kinase reactions) known to communicate the flux changes generated by intracellular ATPases. Under normal conditions and during 20 min of ischemia, the three regions were characterized by different INa, Ito, IKr, IKs, and IKp channel properties. The results indicate that the ATP-sensitive K+ channel is activated by the smallest reduction in ATP in epicardial cells and largest in endocardial cells when cytosolic ADP, AMP, PCr, Cr, Pi, total Mg2+, Na+, K+, Ca2+, and pH diastolic levels are normal. The model predicts that only KATP ionophore (Kir6.2 subunit) and not the regulatory subunit (SUR2A) might differ from endocardium to epicardium. The analysis suggests that during ischemia, the inhomogeneous accumulation of the metabolites in the tissue sublayers may alter in a very irregular manner the KATP channel opening through metabolic interactions with the endogenous PI cascade (PIP2, PIP) that in turn may cause differential action potential shortening among the ventricular myocyte subtypes. The model predictions are in qualitative agreement with experimental data measured under normal and ischemic conditions in rabbit ventricular myocytes. ATP-sensitive K+ channel; creatine and adenylate kinase reactions; phosphatidylinositol phosphates; heart; mathematical model 相似文献
17.
Differential modulation of voltage-dependent K+ currents in colonic smooth muscle by oxidants 总被引:1,自引:0,他引:1
The effect of oxidants on voltage-dependent K+ currents was examined in mouse colonic smooth muscle cells. Exposure to either chloramine-T (Ch-T), an agent known to oxidize both cysteine and methionine residues, or the colon-specific oxidant monochloramine (NH2Cl) completely suppressed the transient outward K+ current (Ito) while simultaneously enhancing the sustained delayed rectifier K+ current (Idr). In contrast, the cysteine-specific oxidants hydrogen peroxide (H2O2) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) exhibited partial and slow suppression of Ito by inducing a shift in channel availability of -18 mV without affecting Idr. After enhancement by NH2Cl or Ch-T, Idr was sensitive to 10 mM tetraethylammonium but not to other K+ channel blockers, suggesting that it represented activation of the resting Idr and not a separate K+ conductance. Extracellular dithiothreitol (DTT) partially reversed the effect of H2O2 and DTNB on Ito but not the actions of NH2Cl and Ch-T on either Idr or Ito. Dialysis of myocytes with GSH (5 mM) or DTT (5 mM) prevented suppression of Ito by H2O2 and DTNB but did not alter the effects of NH2Cl or Ch-T on either Idr or Ito. Ch-T and NH2Cl completely blocked Ito generated by murine Kv4.1, 4.2, and 4.3 in Xenopus oocytes, an effect not reversible by intracellular DTT. In contrast, intracellular DTT reversed the effect of H2O2 and DTNB on the cloned channels. These results suggest that Ito is suppressed via modification of both methionine and cysteine residues, whereas enhancement of Idr likely results from methionine oxidation alone. colon; colitis; redox; ion channel 相似文献
18.
A role for ERK1/2 in EGF- and ATP-dependent regulation of amiloride-sensitive sodium absorption 总被引:3,自引:0,他引:3
Falin R Veizis IE Cotton CU 《American journal of physiology. Cell physiology》2005,288(5):C1003-C1011
Receptor-mediated inhibition of amiloride-sensitive sodium absorption was observed in primary and immortalized murine renal collecting duct cell (mCT12) monolayers. The addition of epidermal growth factor (EGF) to the basolateral bathing solution of polarized monolayers reduced amiloride-sensitive short-circuit current (Isc) by 1525%, whereas the addition of ATP to the apical bathing solution decreased Isc by 4060%. Direct activation of PKC with phorbol 12-myristate 13-acetate (PMA) and mobilization of intracellular calcium with 2,5-di-tert-butyl-hydroquinone (DBHQ) reduced amiloride-sensitive Isc in mCT12 monolayers by 46 ± 4% (n = 8) and 22 ± 2% (n = 8), respectively. Exposure of mCT12 cells to EGF, ATP, PMA, and DBHQ caused an increase in phosphorylation of p42/p44 (extracellular signal-regulated kinase; ERK1/2). Pretreatment of mCT12 monolayers with an ERK kinase inhibitor (PD-98059; 30 µM) prevented phosphorylation of p42/p44 and significantly reduced EGF, ATP, and PMA-induced inhibition of amiloride-sensitive Isc. In contrast, pretreatment of monolayers with a PKC inhibitor (bisindolylmaleimide I; GF109203x; 1 µM) almost completely blocked the PMA-induced decrease in Isc, but did not alter the EGF- or ATP-induced inhibition of Isc. The DBHQ-mediated decrease in Isc was due to inhibition of basolateral Na+-K+-ATPase, but EGF-, ATP-, and PMA-induced inhibition was most likely due to reduced apical sodium entry (epithelial Na+ channel activity). The results of these studies demonstrate that acute inhibition of amiloride-sensitive sodium transport by extracelluar ATP and EGF involves ERK1/2 activation and suggests a role for MAP kinase signaling as a negative regulator of electrogenic sodium absorption in epithelia. mitogen-activated protein kinase; epithelial ion transport; epithelial sodium channel 相似文献
19.
Alvarez de la Rosa D Gimenez I Forbush B Canessa CM 《American journal of physiology. Cell physiology》2006,290(2):C492-C498
Serum- and glucocorticoid-induced kinase 1 (SGK1) is thought to be an important regulator of Na+ reabsorption in the kidney. It has been proposed that SGK1 mediates the effects of aldosterone on transepithelial Na+ transport. Previous studies have shown that SGK1 increases Na+ transport and epithelial Na+ channel (ENaC) activity in the apical membrane of renal epithelial cells. SGK1 has also been implicated in the modulation of Na+-K+-ATPase activity, the transporter responsible for basolateral Na+ efflux, although this observation has not been confirmed in renal epithelial cells. We examined Na+-K+-ATPase function in an A6 renal epithelial cell line that expresses SGK1 under the control of a tetracycline-inducible promoter. The results showed that expression of a constitutively active mutant of SGK1 (SGK1TS425D) increased the transport activity of Na+-K+-ATPase 2.5-fold. The increase in activity was a direct consequence of activation of the pump itself. The onset of Na+-K+-ATPase activation was observed between 6 and 24 h after induction of SGK1 expression, a delay that is significantly longer than that required for activation of ENaC in the same cell line (1 h). SGK1 and aldosterone stimulated the Na+ pump synergistically, indicating that the pathways mediated by these molecules operate independently. This observation was confirmed by demonstrating that aldosterone, but not SGK1TS425D, induced an 2.5-fold increase in total protein and plasma membrane Na+-K+-ATPase 1-subunit abundance. We conclude that aldosterone increases the abundance of Na+-K+-ATPase, whereas SGK1 may activate existing pumps in the membrane in response to chronic or slowly acting stimuli. sodium transport; serum- and glucocorticoid-induced kinase; A6 cells; sodium pump 相似文献
20.
Modulation of K+ currents in monocytes by VCAM-1 and E-selectin on activated human endothelium 总被引:2,自引:0,他引:2
Colden-Stanfield Margaret; Gallin Elaine K. 《American journal of physiology. Cell physiology》1998,275(1):C267
Resting membrane potential (RMP) and whole cell currents wererecorded in human THP-1 monocytes adherent to polystyrene, unstimulated human umbilical vein endothelial cells (HUVECs),lipopolysaccharide (LPS)-treated HUVECs, immobilizedE-selectin, or vascular cell adhesion molecule 1 (VCAM-1)using the patch-clamp technique. RMP after 5 h on polystyrene was24.3 ± 1.7 mV (n = 42) with delayed rectifier K+(Idr) andCl currents(ICl) presentin >75% of the cells. Inwardly rectifying K+ currents(Iir) werepresent in only 14% of THP-1 cells. Adherence to unstimulated HUVECsor E-selectin for 5 h had no effect on Iir orICl but decreasedIdr. Five hoursafter adherence to LPS-treated HUVECs, outward currents were unchanged,but Iir waspresent in 81% of THP-1 cells. A twofold increase inIir and ahyperpolarization (41.3 ± 3.7 mV,n = 16) were abolished by pretreatmentof THP-1 cells with cycloheximide, a protein synthesis inhibitor, orherbimycin A, a tyrosine kinase inhibitor, or by pretreatment of theLPS-treated HUVECs with anti-VCAM-1. Only a brief (15-min) interactionbetween THP-1 cells and LPS-treated HUVECs was required toinduce Iir expression 5 h later. THP-1 cells adherent to VCAM-1 exhibited similarconductances to cells adherent to LPS-treated HUVECs. Thus engagementof specific integrins results in selective modulation of differentK+ conductances. 相似文献