1
|
Witowski J, Breborowicz A, Topley N, Martis L, Knapowski J, Oreopoulos DG. Insulin Stimulates the Activity of Na+/K+-Atpase in Human Peritoneal Mesothelial Cells. Perit Dial Int 2020. [DOI: 10.1177/089686089701700215] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
ObjectiveTo assess the effect of insulin on the Na+/ K+-ATPase expression and activity in human peritoneal mesothelial cells (HPMC).MethodsHPMC were isolated from the omental tissue of non-uremic patients, grown to confluence and rendered quiescent by serum deprivation for 24 hours. The activity of Na+/K+-ATPase was determined by measuring the ouabain-sensitive86Rb uptake. To assess whether the effect of insulin was related to changes in [Na+]i the sodium influx was measured with 22Na and the activity of Na+/K+ -A TPase was assessed in the presence of amiloride. Expression of Na+/K+ -A TPaseα1’ α2 and β1-subunit mRNAs was determined by RT/PCR.ResultsExposure of HPMC to insulin resulted in a time and dose-dependent increase in the Na+/K+-ATPase activity. After 60 minutes the ouabain-sensitive 86Rb up take (cpm/104 cells) was increased from 6650±796 in control cells to 9763±1212 in HPMC exposed to 100 mU/ mL insulin (1.5-fold increase; n=4, P<0.05). In addition, incubation of HPMC with 100 mU/mL insulin resulted in a time-dependent increase in the 22Na influx. Pre-exposure of HPMC to 1 mM amiloride reduced the activity of Na+/K+-A TPase but did not block the stimulatory effect of insulin. RT/PCR analysis revealed that HPMC constitutively expressed α1 and β1-subunit mRNAs while the α2-subunit mRNA was barely detectable. Exposure of HPMC to insulin for up to 24 hours was not associated with any changes in the expression of either α1’ α2 or B1-subunit.ConclusionInsulin stimulates the Na+/K+-ATPase activity in HPMC in a time and dose-dependent manner. This effect appears to mediated by an increase in [Na+]i and is not related to alterations in Na+/K+-ATPase subunit mRNAs expression.
Collapse
Affiliation(s)
- Janusz Witowski
- Department of Pathophysiology, University Medical School, Poznan, Poland
- Institute of Nephrology, University of Wales College of Medicine, Royal Infirmary, Cardiff, Wales
| | | | - Nicholas Topley
- Institute of Nephrology, University of Wales College of Medicine, Royal Infirmary, Cardiff, Wales
| | - Leo Martis
- Baxter Healthcare Corporation, McGaw Park, Illinois, U.S.A
| | - Jan Knapowski
- Department of Pathophysiology, University Medical School, Poznan, Poland
| | | |
Collapse
|
2
|
Sengupta B, Laughlin SB, Niven JE. Comparison of Langevin and Markov channel noise models for neuronal signal generation. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:011918. [PMID: 20365410 DOI: 10.1103/physreve.81.011918] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Revised: 12/16/2009] [Indexed: 05/29/2023]
Abstract
The stochastic opening and closing of voltage-gated ion channels produce noise in neurons. The effect of this noise on the neuronal performance has been modeled using either an approximate or Langevin model based on stochastic differential equations or an exact model based on a Markov process model of channel gating. Yet whether the Langevin model accurately reproduces the channel noise produced by the Markov model remains unclear. Here we present a comparison between Langevin and Markov models of channel noise in neurons using single compartment Hodgkin-Huxley models containing either Na+ and K+, or only K+ voltage-gated ion channels. The performance of the Langevin and Markov models was quantified over a range of stimulus statistics, membrane areas, and channel numbers. We find that in comparison to the Markov model, the Langevin model underestimates the noise contributed by voltage-gated ion channels, overestimating information rates for both spiking and nonspiking membranes. Even with increasing numbers of channels, the difference between the two models persists. This suggests that the Langevin model may not be suitable for accurately simulating channel noise in neurons, even in simulations with large numbers of ion channels.
Collapse
Affiliation(s)
- B Sengupta
- Neural Circuit Design Group, Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK.
| | | | | |
Collapse
|
3
|
Longo N, Scaglia F, Wang Y. Insulin increases the turnover rate of Na+-K+-ATPase in human fibroblasts. Am J Physiol Cell Physiol 2001; 280:C912-9. [PMID: 11245608 DOI: 10.1152/ajpcell.2001.280.4.c912] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin stimulates K+ transport by the Na+-K+-ATPase in human fibroblasts. In other cell systems, this action represents an automatic response to increased intracellular [Na+] or results from translocation of transporters from an intracellular site to the plasma membrane. Here we evaluate whether these mechanisms are operative in human fibroblasts. Human fibroblasts expressed the alpha(1) but not the alpha(2) and alpha(3) isoforms of Na+-K+-ATPase . Insulin increased the influx of Rb+, used to trace K+ entry, but did not modify the total intracellular content of K+, Rb+, and Na+ over a 3-h incubation period. Ouabain increased intracellular Na+ more rapidly in cells incubated with insulin, but this increase followed insulin stimulation of Rb+ transport. Bumetanide did not prevent the increased Na+ influx or stimulation of Na+-K+-ATPase. Stimulation of the Na+-K+-ATPase by insulin did not produce any measurable change in membrane potential. Insulin did not affect the affinity of the pump toward internal Na+ or the number of membrane-bound Na+-K+-ATPases, as assessed by ouabain binding. By contrast, insulin slightly increased the affinity of Na+-K+-ATPase toward ouabain. Phorbol esters did not mimic insulin action on Na+-K+-ATPase and inhibited, rather than stimulated, Rb+ transport. These results indicate that insulin increases the turnover rate of Na+-K+-ATPases of human fibroblasts without affecting their number on the plasma membrane or modifying their dependence on intracellular [Na+].
Collapse
Affiliation(s)
- N Longo
- Division of Medical Genetics, Department of Pediatrics, Emory University, 2040 Ridgewood Drive, Atlanta, GA 30322, USA.
| | | | | |
Collapse
|
4
|
Coury LA, McGeoch JE, Guidotti G, Brodsky JL. The yeast Saccharomyces cerevisiae does not sequester chloride but can express a functional mammalian chloride channel. FEMS Microbiol Lett 1999; 179:327-32. [PMID: 10518733 DOI: 10.1111/j.1574-6968.1999.tb08745.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Chloride uptake into yeast was measured as a function of pH. A small amount of uptake was seen at pH values of 3.0 and 4.0; at pH 6.0 chloride uptake was substantially less than the uptake of phosphate and rubidium. Because chloride uptake is inefficient, we expressed the putative mammalian chloride channel, pI(Cln), in yeast and observed a chloride-selective current when total membrane protein was reconstituted into lipid bilayers. The current was inhibited by a specific chloride channel blocker, 5-nitro-2-(3-phenylpropylamino)-benzoic acid. These results suggest that yeast may serve as a means to characterize chloride channels from other organisms.
Collapse
Affiliation(s)
- L A Coury
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA 15213-2500, USA
| | | | | | | |
Collapse
|
5
|
Brown RL, Haley TL, West KA, Crabb JW. Pseudechetoxin: a peptide blocker of cyclic nucleotide-gated ion channels. Proc Natl Acad Sci U S A 1999; 96:754-9. [PMID: 9892706 PMCID: PMC15209 DOI: 10.1073/pnas.96.2.754] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Ion channels activated by the binding of cyclic nucleotides first were discovered in retinal rods where they generate the cell's response to light. In other systems, however, it has been difficult to unambiguously determine whether cyclic nucleotide-dependent processes are mediated by protein kinases, their classical effector enzymes, or cyclic nucleotide-gated (CNG) ion channels. Part of this difficulty has been caused by the lack of specific pharmacological tools. Here we report the purification from the venom of the Australian King Brown snake of a peptide toxin that inhibits current through CNG channels. This toxin, which we have named Pseudechetoxin (PsTx), was purified by cation exchange and RP-HPLC and has a molecular mass of about 24 kDa. When applied to the extracellular face of membrane patches containing the alpha-subunit of the rat olfactory CNG channel, PsTx blocked the cGMP-dependent current with a Ki of 5 nM. Block was independent of voltage and required only a single molecule of toxin. PsTx also blocked CNG channels containing the bovine rod alpha-subunit with high affinity (100 nM), but it was less effective on the heteromeric version of the rod channel (Ki approximately 3 microM). We have obtained N-terminal and partial internal sequence data and the amino acid composition of PsTx. These data indicate that PsTx is a basic protein that exhibits some homology with helothermine, a toxin isolated from the venom of the Mexican beaded lizard. PsTx promises to be a valuable pharmacological tool for studies on the structure and physiology of CNG channels.
Collapse
Affiliation(s)
- R L Brown
- Neurological Sciences Institute, Oregon Health Sciences University, 1120 NW 20th Avenue, Portland, OR 97209, USA.
| | | | | | | |
Collapse
|
6
|
Santy LC, Guidotti G. Expression of a single gene produces both forms of skeletal muscle cyclic nucleotide-gated channels. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 273:E1140-8. [PMID: 9435530 DOI: 10.1152/ajpendo.1997.273.6.e1140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Cyclic nucleotide-gated cation channels in skeletal muscle are responsible for insulin-activated sodium entry into this tissue (J. E. M. McGeoch and G. Guidotti. J. Biol. Chem. 267: 832-841, 1992). These channels have previously been isolated from rabbit skeletal muscle by 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) affinity chromatography, which separates them into two populations differing in nucleotide affinity [L. C. Santy and G. Guidotti. Am. J. Physiol. 271 (Endocrinol. Metab. 34): E1051-E1060, 1996]. In this study, a polymerase chain reaction approach was used to identify skeletal muscle cyclic nucleotide-gated channel cDNAs. Rabbit skeletal muscle expresses the same cyclic nucleotide-gated channel as rabbit aorta (M. Biel, W. Altenhofen, R. Hullin, J. Ludwig, M. Freichel, V. Flockerzi, N. Dascal, U. B. Kaupp, and F. Hofmann. FEBS Lett. 329: 134-138, 1993). The entire cDNA for this gene was cloned from rabbit skeletal muscle and an antiserum to this protein produced. Expression of this cDNA produces a 63-kDa protein with cyclic nucleotide-gated channel activity. A similarly sized immunoreactive protein is present in sarcolemma. Purification of the expressed channels reveals that this single gene produces both native skeletal muscle channel populations.
Collapse
Affiliation(s)
- L C Santy
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA
| | | |
Collapse
|
7
|
McGeoch JE, Guidotti G. A 0.1-700 Hz current through a voltage-clamped pore: candidate protein for initiator of neural oscillations. Brain Res 1997; 766:188-94. [PMID: 9359602 DOI: 10.1016/s0006-8993(97)00618-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A protein of mass 7643 Da and sequence identical to that of subunit c, the pore part, of the mitochondrial adenosine triphosphate synthase complex, was co-purified with cholesterol in crystals formed from a chloroform/methanol extract of bovine brain gray matter plasma membranes. Reconstitution of the protein-containing crystals in phospholipid bilayers and assay of current by patch-clamp analysis, showed an oscillating cation current at constant voltage, typically of frequency 0.5-200 Hz. The ceroid-lipofuscinoses state in mammals and man (Batten disease), in which subunit c accumulates in lysosomes, affords a rich source of the protein. Pure subunit c from affected sheep liver (in the absence of cholesterol) was also assayed, the current displaying identical sodium oscillations to those of brain crystals. The results suggest that if a protein similar to subunit c resides in the plasma membrane of neural cells, it could be responsible for spontaneous oscillations in brain tissue. The relevance of these results to the pathogenesis of Batten disease is discussed.
Collapse
Affiliation(s)
- J E McGeoch
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | | |
Collapse
|
8
|
Santy LC, Guidotti G. Reconstitution and characterization of two forms of cyclic nucleotide-gated channels from skeletal muscle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 271:E1051-60. [PMID: 8997225 DOI: 10.1152/ajpendo.1996.271.6.e1051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A cyclic nucleotide-gated channel present in skeletal muscle plasma membrane has previously been identified as being responsible for insulin-activated sodium entry into muscle cells (J. E. M. McGeoch and G. Guidotti. J. Biol. Chem. 267:832-841, 1992). We have isolated this channel activity to further study and characterize it. The channel was solubilized from rabbit skeletal muscle sarcolemma and functionally reconstituted into phospholipid vesicles, as assayed by patch-clamp analysis of the reconstituted proteins. Channel activity was isolated by 8-bromo-guanosine 3',5'-cyclic monophosphate affinity chromatography, producing two distinct peaks of cyclic nucleotide-gated channel activity. These two types of channel activity differ in guanosine 3',5'-cyclic monophosphate affinity and in the ability to be opened by adenosine 3',5'-cyclic monophosphate. The cyclic nucleotide-gated channel from rod outer segments also forms two peaks of activity when purified in this manner. The presence of two forms of channel activity could have implications for the mechanism of insulin-activated sodium entry.
Collapse
Affiliation(s)
- L C Santy
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA
| | | |
Collapse
|
9
|
|
10
|
Abstract
Insulin increases the volume of isolated hepatocytes and cells in perfused livers, but effects of the hormone on the volume of fat or muscle cells have not been demonstrated. Exogenous amino acids may stimulate swelling of liver cells and induce insulin-like effects on hepatic protein metabolism; however, swelling of liver cells can be induced by some treatment that do not induce insulin-like metabolic responses. Exogenous amino acids also influence protein metabolism of fat and muscle cells, but no relationship with cell volume has been established and no corresponding effects on metabolism of carbohydrates or lipids have been observed. Three families of mitogen-activated protein kinases are activated after changes in extracellular osmolarity but they appear to play little or no role in the metabolic actions of insulin. Direct evidence against a metabolic role for the extracellular signal-regulated kinases ERK-1 and ERK-2 is discussed. The c-Jun N-terminal kinases (also called stress-activated protein kinases) and the mammalian homologs of the yeast Hog protein kinase are strongly activated by environmental stresses associated with catabolic metabolism. We conclude that cell volume and protein metabolism may be correlated in liver but there is no compelling evidence that the effects of insulin on metabolism of liver, fat, or muscle cells can be accounted for by changes in cell volume. The effects of insulin on cell volume may represent a discrete aspect of the complete physiological response rather than an obligatory intermediate step in metabolic signalling.
Collapse
Affiliation(s)
- R Zhande
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada
| | | |
Collapse
|
11
|
Longo N. Insulin stimulates the Na+,K(+)-ATPase and the Na+/K+/Cl- cotransporter of human fibroblasts. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1281:38-44. [PMID: 8652602 DOI: 10.1016/0005-2736(96)00004-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Insulin regulation of K+ (Rb+) transport was investigated in cultured human fibroblasts using a non-radioactive method which allows the simultaneous determination of the intracellular concentration of other monovalent cations. Insulin stimulated Rb+ influx through the Na+,K(+)-ATPase and the Na+/K(+)/Cl- cotransporter in human fibroblasts. Insulin stimulation was very rapid and maximal effect was observed within 10 min. Insulin stimulation of Rb+ uptake via the Na+,K(+)-ATPase and the Na+/K(+)/Cl- cotransporter was dose-dependent, with half-maximal stimulation at 2-3 nM of hormone. Insulin increased the V(max) of both transporters involved, affecting only minimally their Km. In other cells, insulin stimulates the Na+,K(+)-pump by increasing Na+ availability through the Na+/H+ exchanger. In human fibroblasts, insulin stimulation of Na+,K(+)-ATPase occurred in the presence of ethyl-isopropyl amiloride, an inhibitor of the Na+/H+ exchanger, and without sustained changes in intracellular[Na+]. By contrast, insulin action on Na+,K(+)-ATPase was impaired by the protein kinase inhibitors staurosporine and genistein. These results indicate that, in human fibroblasts, insulin stimulates both the Na+,K(+)-ATPase and the Na+/K+/Cl- cotransporter, that stimulation of the Na+,K(+)-ATPase occurs in the absence of changes in intracellular [Na+], and that protein kinase activity is essential for this insulin action.
Collapse
Affiliation(s)
- N Longo
- Department of Pediatrics, Emory University, Atlanta, GA 30322, USA
| |
Collapse
|
12
|
Lavoie L, Roy D, Ramlal T, Dombrowski L, Martín-Vasallo P, Marette A, Carpentier JL, Klip A. Insulin-induced translocation of Na+-K+-ATPase subunits to the plasma membrane is muscle fiber type specific. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 270:C1421-9. [PMID: 8967443 DOI: 10.1152/ajpcell.1996.270.5.c1421] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We have previously shown that an acute insulin treatment induces redistribution of the alpha 2- and beta 1- isoforms of the Na+-K+-ATPase from intracellular membranes to plasma membranes detected on subcellular fractionation of mixed muscles and immunoblotting with isoform-specific antibodies (H. S. Hundal et al. J. Biol. Chem. 267: 5040-5043, 1992). In the present study we give both biochemical and morphological evidence that this insulin effect is operative in muscles composed mostly of oxidative (red) fibers but not in muscles composed mostly of glycolytic (white) fibers. The redistribution of the Na+-K+-ATPase alpha 2- and beta 1-isoforms after insulin injection was detected in membranes isolated from and muscles (soleus, red gastrocnemius, red rectus femoris, and red vastus lateralis) but not in membranes from white muscles (white gastrocnemius, tensor fasciae latae, white rectus femoris, and white vastus lateralis). After insulin injection, the potassium-dependent 3-O-methylfluorescein phosphatase activity of the enzyme was higher by 22% in the plasma membrane-enriched fraction and lower by 15% in the internal membrane fraction isolated from red but not from white muscles. Quantitative immunoelectron microscopy of ultrathin muscle cryosections showed that in vivo insulin stimulation augmented the density of Na+-K+-ATPase alpha 2- and beta 1- isoforms at the plasma membrane of soleus muscle by 80 and 124%, respectively, with no change in white gastrocnemius muscle. The effect of insulin to increase the content of Na+-K+-ATPase alpha 2- and beta 1-subunits in isolated plasma membranes was still observed when glycemia was prevented from dropping by using hyperinsulinemic-euglycemic clamps. We conclude that the insulin-induced redistribution of the alpha 2- and beta 1-isoforms of the Na+-K+-ATPase from an intracellular pool to the plasma membrane in restricted to oxidative fiber-type skeletal muscles. This may be related to the selective expression of beta 1-subunits in these fibers and implies that the beta 2-subunit, typical of glycolytic muscles, does not sustain translocation of alpha 2 beta 2-complexes.
Collapse
Affiliation(s)
- L Lavoie
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
| | | | | | | | | | | | | | | |
Collapse
|
13
|
Abstract
Cyclic nucleotide-gated (CNG) channels are nonselective cation channels that are activated by direct interaction of the second messengers cAMP and cGMP. Once activated, they provide for membrane depolarization and Ca2+ influx into cells. The functions of CNG channels are tightly coupled to the mechanisms by which cAMP and cGMP are regulated in neurons, namely through activation of G-protein–coupled membrane receptors and through the nitric oxide/guanylyl cyclase signaling system. These functions are best understood in sensory neurons of the vertebrate visual and olfactory system, where CNG channels are critical components of the signal transduction apparatus. The family of known CNG channels is expanding, and there is now increasing evidence that these channels are also present in many other areas of the nervous system. Based on their role in sensory neurons, a functional framework for the role of CNG channels in the CNS is provided.
Collapse
Affiliation(s)
- Frank Zufall
- Section of Neurobiology Yale University School of Medicine New Haven, Connecticut
| |
Collapse
|
14
|
Sargeant RJ, Liu Z, Klip A. Action of insulin on Na(+)-K(+)-ATPase and the Na(+)-K(+)-2Cl- cotransporter in 3T3-L1 adipocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 269:C217-25. [PMID: 7631748 DOI: 10.1152/ajpcell.1995.269.1.c217] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The Na(+)-K(+)-ATPase presents several different isoforms of its alpha- and beta-subunits. We detected alpha 1- and beta 1-mRNA transcripts and polypeptides in 3T3-L1 fibroblasts; during differentiation into adipocytes, alpha 1-mRNA decreased, alpha 2-mRNA was induced, beta 1-mRNA dropped to undetectable levels, and beta 2-mRNA was never expressed, suggesting that 3T3-L1 adipocytes may express an unidentified Na(+)-K(+)-ATPase beta-subunit isoform. Insulin rapidly increased ion pump activity [ouabain-sensitive 86Rb+(K+) uptake] in 3T3-L1 fibroblasts and adipocytes without changing the plasma membrane concentration of alpha 1- or alpha 2-subunits as determined by subcellular membrane fractionation and immunoblotting or by [3H]ouabain binding to intact cells. Monensin, which raises the concentration of intracellular Na+, increased Na(+)-K+ pump activity, and no further stimulation was achieved with insulin. The stimulation of the pump by insulin was reduced by bumetanide, an inhibitor of the Na(+)-K(+)-2Cl- cotransporter, and was prevented by omission of extracellular Cl-. Insulin increased both ouabain-sensitive and bumetanide-sensitive 86Rb+(K+) uptake. These results suggest that insulin activation of the Na(+)-K(+)-ATPase in 3T3-L1 adipocytes is mediated by an elevation in intracellular Na+ that is likely the consequence of Na(+)-K(+)-2Cl- cotransporter activation.
Collapse
Affiliation(s)
- R J Sargeant
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
| | | | | |
Collapse
|
15
|
Pancrazio JJ. Ion channel events simulated with the program SIMSTATE. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 1995; 46:165-174. [PMID: 7540964 DOI: 10.1016/0169-2607(94)01618-p] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Ion channel transitions between conducting (open) and non-conducting (closed) states are often described in terms of a chemical kinetic model, where the rate constants describing the transitions between states can be derived by analysing a data record and measuring channel dwell times. In this paper, a menu-driven program for IBM-compatible microcomputers, SIMSTATE, is described which permits simulations of one or more channels according to a user-specified set of transition rates. Rates can be constant, voltage- or ligand-activated, exhibit co-operativity, or dependent on the calcium concentration resulting from the opening of one or more nearby Ca channels. To illustrate the functionality of SIMSTATE, open and closed events are simulated for a well-known Ca channel model and an example of co-operative gating is examined. Furthermore, the control of a Ca-dependent K channel by a nearby Ca channel, which also opens and closes according to a user-specified transition rates, is described. Potential uses for SIMSTATE as a tool for theoretical analysis, education and experimental design are discussed.
Collapse
Affiliation(s)
- J J Pancrazio
- Department of Anesthesiology, University of Virginia Health Sciences Center, Charlottesville 22908, USA
| |
Collapse
|
16
|
Sampson SR. Activation of protein kinase C mediates insulin regulation of the Na-K pump in cultured skeletal muscle. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1995; 381:47-56. [PMID: 8867822 DOI: 10.1007/978-1-4615-1895-2_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- S R Sampson
- Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| |
Collapse
|
17
|
Marette A, Krischer J, Lavoie L, Ackerley C, Carpentier JL, Klip A. Insulin increases the Na(+)-K(+)-ATPase alpha 2-subunit in the surface of rat skeletal muscle: morphological evidence. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 265:C1716-22. [PMID: 8279532 DOI: 10.1152/ajpcell.1993.265.6.c1716] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The cellular localization of the alpha 2-subunit of the Na(+)-K(+)-ATPase was defined by immunoelectron microscopy, and the effect of insulin on the amount of alpha 2-immunoreactive subunits on the cell surface was quantitated. Two protocols were used for tissue fixation and immunolocalization. Protocol 1 was characterized by fixation with 2% paraformaldehyde, use of a monoclonal antibody, and detection with 3-nm-diameter gold-labeled Fab fragments or 10-nm gold-labeled immunoglobulin G. Protocol 2 was characterized by fixation with 4% paraformaldehyde plus 0.1% glutaraldehyde, use of a polyclonal antibody, and detection with 10-nm gold-labeled protein A. In control muscle, the alpha 2-subunit of the Na(+)-K(+)-ATPase was present at the plasma membrane and in intracellular tubular and vesicular structures located in subsarcolemmal and triadic regions. Acute insulin stimulation increased the number of immunolabeled alpha 2-subunits in the plasma membrane after both fixation protocols. The gain in the plasma membrane ranged from 1.5- to 3.7-fold and was significant at the level of P < 0.005. These results provide morphological quantitative evidence that the alpha 2-subunit of the Na(+)-K(+)-ATPase is present both at the plasma membrane and intracellularly in mammalian skeletal muscle and that insulin acutely increases its abundance in the muscle surface.
Collapse
Affiliation(s)
- A Marette
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
| | | | | | | | | | | |
Collapse
|