Insulin action on membrane potential and glucose uptake: effects of high potassium

1985 ◽  
Vol 249 (1) ◽  
pp. E17-E25
Author(s):  
K. Zierler ◽  
E. M. Rogus ◽  
R. W. Scherer ◽  
F. S. Wu
Keyword(s):  
Membrane Potential ◽  
Insulin Action ◽  
Potassium Concentration ◽  
Electrical Potential ◽  
Cell Swelling ◽  
Electrical Potential Difference ◽  
High Potassium ◽  
High K ◽  
External Potassium ◽  
Stimulation Of

These experiments were designed to test the hypothesis that insulin-induced hyperpolarization is a link in the chain of events leading to stimulation of glucose transport. External potassium concentration, [K+]o, was increased by equimolar substitution of KCl for NaCl, a method known to cause cell swelling, and by substitution of [K+]o for [Na+]o with maintenance of constant [K+]o X [Cl-]o product, a method that does not cause cell swelling. When there was constant KCl product, even at 76.8 meq [K+]o insulin continued to hyperpolarize, although by only approximately 44% as much as in normal [K+]o, and insulin-stimulated 2-deoxyglucose uptake was only approximately 60% of that at normal [K+]o. With equimolar substitution of KCl for NaCl: electrical potential difference across cell membranes of surface fibers of rat caudofemoralis muscle decreased with logarithm [K+]o, in the presence or absence of insulin. Insulin-induced hyperpolarization decreased as [K+]o increased and disappeared at 36 mM [K+]o. The amount of insulin bound to its receptors in 1 h was not affected by [K+]o over the range studied. Insulin effects on membrane potential and on 2-deoxyglucose uptake, as both were altered by [K+]o, correlated well. As the probe moved in depth through the first six fibers there was stepwise decrease in depolarization in high [K+]o in the absence of insulin. Insulin hyperpolarized the deepest of these fibers, even when it did not hyperpolarize the outermost. The decrease in insulin-induced hyperpolarization as [K+]o increases is consistent with the hypothesis that insulin hyperpolarizes by decreasing the ratio PNa/PK.

Effects of changes in electrical potential difference on tubular potassium transport

1980 ◽  
Vol 238 (3) ◽  
pp. F235-F246 ◽  
Author(s):  
E. Garcia-Filho ◽  
G. Malnic ◽  
G. Giebisch
Keyword(s):  
Potassium Concentration ◽  
Electrical Potential ◽  
Potential Drop ◽  
Plasma Potassium ◽  
Potential Difference ◽  
Electrical Potential Difference ◽  
High Potassium ◽  
Transepithelial Potential ◽  
Wide Range ◽  
Potassium Secretion

To assess directly the role of the transepithelial potential difference (PD) on potassium concentration differences across distal tubular epithelium, continuous and stationary microperfusion experiments were done in tubules voltage-clamped over a wide range of lumen-negative potentials. Potassium was measured either chemically or in situ by potassium-sensitive microelectrodes. Distal cell PD measurements show that most of the potential drop induced by luminal current injection occurred across the luminal cell membrane. Experiments were done in rats either on a control or on a high potassium diet and after amiloride administration. Luminal potassium was highly sensitive to imposed electrical potential changes, attainment of a new steady-state intraluminal potassium concentration was rapid (less than 1 s), and higher luminal potassium concentrations were observed in animals in which potassium secretion had been stimulated. Similar slopes of tubular fluid-to-plasma potassium ratios versus transepithelial potential differences were observed in all experiments. All slopes intersected, at zero PD, at a luminal tubular fluid-to-plasma concentration ratio in excess of unity, indicating the presence of an active component of potassium secretion.

Relation of Intracellular K+ and Steroidogenesis in Isolated Adrenal Zona Glomerulosa and Fasciculata Cells

1975 ◽  
Vol 49 (1) ◽  
pp. 13-26
Author(s):  
F. A. Mendelsohn ◽  
C. Mackie
Keyword(s):  
Potassium Concentration ◽  
Zona Glomerulosa ◽  
Zona Fasciculata ◽  
High Potassium ◽  
External Potassium ◽  
Glomerulosa Cells ◽  
Unit Gravity Sedimentation ◽  
Zona Glomerulosa Cells ◽  
Stimulation Of

1. Intracellular K+ content, water spaces and corticosterone output were measured in isolated zona glomerulosa and zona fasciculata-reticularis cell suspensions of rat adrenal cortex, after incubations in vitro under conditions designed to alter steroidogenesis. 2. Intracellular K+ of unpurified zona glomerulosa cells was not altered after stimulation of corticosterone output with serotonin. Similarly, with zona glomerulosa cells purified by unit gravity sedimentation, no change in intracellular K+ was detected after stimulation of steroidogenesis with serotonin or angiotensin II. 3. In high-potassium medium (final concentration 84 mmol/l), parallel increases in intracellular K+ and corticosterone output were observed with both unpurified and purified zona glomerulosa cells. However, a similar increase in intracellular K+ also occurred in high-potassium medium with zona fasciculata cells, whose steroid output is unresponsive to external potassium concentration ([K+]). 4. Ouabain at 10−5 mol/l depressed the intracellular [K+] of glomerulosa cells but did not alter basal or stimulated corticosterone output. Similar results were obtained with fasciculata cells. 5. Ouabain at 5×10−4 mol/l further depressed intracellular [K+] of glomerulosa cells and inhibited basal and stimulated corticosterone output. However, this concentration of ouabain also inhibited steroidogenesis in fasciculata cells. 6. These results demonstrate a variety of situations where changes in intracellular [K+] are dissociated from those in corticosterone output and indicate that intracellular [K+] cannot be the sole mechanism regulating steroidogenesis under these conditions.

Ability to Light-Induced Conductance Change of Arthropod Visual Cell Membrane, Indirectly Depending on Membrane Potential, during Depolarization by External Potassium or Ouabain

1977 ◽  
Vol 32 (9-10) ◽  
pp. 855-869 ◽  
Author(s):  
H. Stieve ◽  
M. Bruns ◽  
H. Gaube
Keyword(s):  
Membrane Potential ◽  
Potassium Concentration ◽  
Time Lag ◽  
Reference Value ◽  
Membrane Conductance ◽  
Visual Cell ◽  
Half Time ◽  
Astacus Leptodactylus ◽  
High Potassium ◽  
External Potassium

Abstract Light responses (ReP) and pre-stimulus membrane potential (PM P) and conductance of photoreceptors of Astacus leptodactylus and Limulus polyphemus (lateral eye) were recorded and changes were observed when the photoreceptor was depolarized by the action of external ouabain or high potassium concentration application.1 mм/1 ouabain application causes a transient increase of PMP and ReP in Limulus, followed by a decrease which is faster for the ReP (half time 34 min) than for the PMP (half time 80 min). Irreversible loss of excitability occurs when the PM P is still ca. 40% of the reference value.In both preparations high external potassium concentration leads to total depolarization (beyond zero line to +10 - +20mV) of the PMP and after a time lag of 10 min also to a loss of excitability (intracellular recording). In extracellular recordings (Astacus) the excitability remains at a low level of 15%. The effects are reversible and are similar whether no or 10% external sodium is present. In all experiments the light-induced changes of membrane conductance are about parallel to those of the light response.The fact that the ability of the photosensoric membrane to undergo light-induced conductance changes is membrane potential-dependent is discussed, leading to the explanation that dipolar membrane constituents such as channel forming molecules (probably not rhodopsin) have to be ordered by the m embrane potential to keep the membrane functional for the photosensoric action.

Effects of flow rate and potassium intake on distal tubular potassium transfer

1975 ◽  
Vol 228 (4) ◽  
pp. 1249-1261 ◽  
Author(s):  
RN Khuri ◽  
WN Strieder ◽  
G Giebisch
Keyword(s):  
Flow Rate ◽  
Electrical Potential ◽  
Isotonic Saline ◽  
Distal Tubule ◽  
Sodium Reabsorption ◽  
Electrical Potential Difference ◽  
High Potassium ◽  
Flow Rates ◽  
Potassium Intake ◽  
Potassium Secretion

Potassium transport was studied across proximal and distal tubular epithelium in rats on a normal, low- and high-potassium intake during progressive loading with isotonic saline (150 mM) or a moderately hypersomotic urea (200 mM) sodium chloride (100 mM) solution. Free-flow micropuncture and recollection techniques were used during the development of diruesis and tubular fluid (TF) analyzed for inulin-14C, potassium (K) and sodium (Na). Tubular puncture sites were localized by neoprene filling and microdissection. During the large increase in tubular flow rates (10 times): 1) fractional potassium reabsorption fell along the proximal tubule, 2) TFk along the distal tubule remained constant and independent of flow rate in control and high-k rats; thus, net potassium secretion increased in proportion to and was limited by flow rate. 3) In low-K rats TF k fell; with increasing flow rates distal K secretion was not effectively stimulated. 4) Distal tubular sodium reabsorption increased in all animals with flow rate, but tubular Na-K exchange ratios varied greatly. It is suggested that whenever sodium delivery stimulates distal tubular potassium secretion it does so by 1) increasing volume distal tubular potasssium secretion and by 2) augmenting the transepithelial electrical potential difference (lumen negative).

The Effect of External Potassium Ions on the Electrical Potential Measured Across the Gills of the Teleost, Dormitator Maculatus

1974 ◽  
Vol 61 (2) ◽  
pp. 277-283
Author(s):  
DAVID H. EVANS ◽  
JEFFREY C. CARRIER ◽  
MARGARET B. BOGAN
Keyword(s):  
Sea Water ◽  
Electrical Potential ◽  
Potassium Ions ◽  
Sodium Efflux ◽  
Electrical Potentials ◽  
External Potassium ◽  
Potassium Influx ◽  
Sodium Extrusion ◽  
Sufficient Magnitude ◽  
Stimulation Of

1. A technique has been developed for the measurement of electrical potentials (TGP's) across the gills of free-swimming, Dormitator maculatus. 2. Transfer of fish to various KCl solutions is correlated with changes in the TGP, which are not of sufficient magnitude to account for the known potassium stimulation of sodium efflux from this species. 3. Transfer to potassium-free sea water results in little or no change in TGP while previous results have shown that such a transfer is correlated with a 22% reduction of sodium efflux. 4. Transfer to fresh water results in a reduction of TGP from +17 mV (inside positive) to -36 mV which is sufficient to account for the instantaneous reduction in sodium efflux previously shown for this species. 5. It is concluded that while changes in TGP can account for the ‘Na-free effect’ in D. maculatus they cannot account for the potassium effects on sodium extrusion. This supports the previous conclusion that sodium efflux and potassium influx are chemically linked in this species.

scholarly journals Relative Ion Permeabilities in the Crayfish Giant Axon Determined from Rapid External Ion Changes

1967 ◽  
Vol 50 (7) ◽  
pp. 1929-1953 ◽  
Author(s):  
Alfred Strickholm ◽  
B. Gunnar Wallin
Keyword(s):  
Membrane Potential ◽  
Potassium Level ◽  
Potassium Concentration ◽  
Giant Axon ◽  
Resting Potential ◽  
Resting Membrane Potential ◽  
Constant Field ◽  
Appreciable Effect ◽  
Ion Concentrations ◽  
External Potassium

The changes in membrane potential of isolated, single crayfish giant axons following rapid shifts in external ion concentrations have been studied. At normal resting potential the immediate change in membrane potential after a variation in external potassium concentration is quite marked compared to the effect of an equivalent chloride change. If the membrane is depolarized by a maintained potassium elevation, the immediate potential change due to a chloride variation becomes comparable to that of an equivalent potassium change. There is no appreciable effect on membrane potential when external sodium is varied, at normal or at a depolarized membrane potential. Starting from the constant field equation, expressions for the permeability ratios PCl/PK, PNa/PK, and for intracellular potassium and chloride concentrations are derived. At normal resting membrane potential, PCl/PK is 0.13 but at a membrane potential of -53 mv (external potassium level increased about five times) it is 0.85. The intracellular concentrations of potassium and chloride are estimated to be 233 and 34 mM, respectively, and it is pointed out that this is not compatible with ions distributed in a Nernst equilibrium across the membrane. It is also stressed that the information given by a plot of membrane potential vs. the logarithm of external potassium concentrations is very limited and rests upon several important assumptions.

Sex differences in membrane potential in the intact perfused rat liver

1988 ◽  
Vol 255 (6) ◽  
pp. G822-G825 ◽  
Author(s):  
R. A. Weisiger ◽  
J. G. Fitz
Keyword(s):  
Sex Differences ◽  
Plasma Membrane ◽  
Membrane Potential ◽  
Electrical Potential ◽  
Hepatic Uptake ◽  
Female Rats ◽  
Electrical Potential Difference ◽  
Bicarbonate Buffer ◽  
Male And Female Rats ◽  
Negative Membrane Potential

The electrical potential difference across the plasma membrane was compared in paired livers from male and female rats perfused single-pass with Krebs-bicarbonate buffer. Variability in the membrane potential measured for different cells within the same liver was small (SD = 1.3 mV). The mean membrane potential was 5.1 mV more negative for male livers than for female livers (-30.3 +/- 0.6 vs. -25.2 +/- 1.0 mV, P less than 0.001), and the male liver had a more negative membrane potential than the female liver in all nine pairs studied. No correlation between membrane potential and perfusion rate was seen. Variability among female livers was more than twice as great (range -19.6 to -30.0 mV) as for male livers (range -26.7 to -31.9 mV). These results suggest that hepatic membrane potential may be modulated by sex hormone levels, which are more variable in female animals. Because the hepatic uptake of bile acids such as taurocholate and organic anions such as bilirubin may involve net movement of electrical charge across the plasma membrane, the current results may explain previously reported sex differences in the uptake of these and other electrogenically transported molecules.

Stimulation of HCO3- transport in isolated proximal bullfrog duodenum by prostaglandins

1980 ◽  
Vol 239 (3) ◽  
pp. G198-G203 ◽  
Author(s):  
G. Flemstrom
Keyword(s):  
Electrical Potential ◽  
Potential Difference ◽  
Electrical Potential Difference ◽  
Morphological Examination ◽  
Minimal Concentration ◽  
Dependent Transport ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Stimulation Of

An in vitro preparation of proximal duodenum from the bullfrog transported alkali into the luminal solution (approximately 1 mueq x h-1 x cm-2) and generated a transepithelial electrical potential difference (5-10 mV, lumen negative). Transport was inhibited by 2,4-dinitrophenol (10(-5) M), CN- (5 X 10(-3) M), indomethacin (5 X 10(-5) M), and acetazolamide (5 X 10(-3) M) indicating that metabolism is required. Both alkali transport and the electrical potential difference showed a dose-dependent increase on administration of the prostaglandins E2, 16,16-dimethyl E2, and F2 alpha. The minimal concentration stimulating transport was lower with the E-type prostaglandins (10(-8) M than with F2 alpha (10(-6) M), and the former also produced greater maximal responses. In addition to metabolic-dependent transport of alkali, there was passive transmucosal migration of HCO3-, amounting to approximately 40% of basal (unstimulated) transport and sensitive to variation of the transmucosal hydrostatic pressure. Morphological examination showed that the preparation is devoid of Brunner glands. Stimulation of duodenal epithelial HCO3- transport by prostaglandins may contribute to their previously demonstrated ability to prevent duodenal ulceration.

Fluorescence imaging study of organic anion transport from renal proximal tubule cell to lumen

1996 ◽  
Vol 271 (3) ◽  
pp. F508-F520 ◽  
Author(s):  
D. S. Miller ◽  
S. Letcher ◽  
D. M. Barnes
Keyword(s):  
Steady State ◽  
Organic Anion ◽  
Electrical Potential ◽  
Imaging Study ◽  
Anion Transport ◽  
Electrical Potential Difference ◽  
Proximal Tubule Cell ◽  
Organic Anion Transport ◽  
Uptake Mechanism ◽  
High Potassium

The mechanisms driving organic anion transport from cell to lumen were studied in intact killifish proximal tubules using fluorescence microscopy. Three fluorescent substrates were used as follows: 1) fluorescein (FL); 2) carboxyfluorescein (CF), generated intracellularly from carboxyfluorescein diacetate (CFDA); and 3) bimane-S conjugates, generated intracellularly by conjugation of monochlorobimane (MCB) with glutathione (GSH) and subsequent metabolism. The latter two substrates bypassed the basolateral uptake mechanism, allowing direct study of luminal transport mechanisms. At steady state, for all three substrates, luminal fluorescence was two to three times higher than cellular fluorescence. With FL as substrate, addition of p-aminohippurate (PAH) or probenecid to the incubation medium reduced cellular and luminal fluorescence to roughly the same extent. With CFDA or MCB as substrate, PAH and probenecid only slightly reduced cellular fluorescence but greatly reduced luminal fluorescence. MCB blocked transport of FL from cell to lumen; CFDA blocked transport of bimane-S conjugates from cell to lumen. Finally, depolarizing tubule cells with high-potassium medium did not affect the steady-state lumen-to-cell distribution of FL, CF, or bimane-S conjugates. These results show that organic anion transport from cell to lumen is mediated and uphill but not sensitive to the electrical potential difference across the luminal membrane.

POTASSIUM STIMULATION OF OXIDATION AND PHOSPHORYLATION IN PIGEON-MUSCLE MITOCHONDRIA

1966 ◽  
Vol 44 (8) ◽  
pp. 1127-1132 ◽  
Author(s):  
G. J. Marcus ◽  
J. F. Manery
Keyword(s):  
Potassium Concentration ◽  
Sodium Concentration ◽  
Oxygen Electrode ◽  
High Potassium ◽  
Muscle Mitochondria ◽  
High Sodium ◽  
Glucose Phosphate ◽  
Minute Period ◽  
The Mean ◽  
Stimulation Of

With alpha-ketoglutarate as substrate and a hexokinase – glucose phosphate acceptor system, the rates of oxidation and phosphorylation of pigeon-muscle mitochondria were measured in media in which the proportion of potassium to sodium was varied. As the potassium concentration was elevated from 0 to about 70 mmoles/liter, the sodium concentration was correspondingly decreased. With both the Warburg apparatus and the polarograph, the rate of respiration was shown to rise as the proportion of potassium in the medium was increased. The mean rate in the high-potassium media was 130% of that in the high-sodium media over the five-minute period measured with the oxygen electrode, and 135% over the thirty-minute period measured by Warburg manometry. The rate of phosphorylation was stimulated to an even greater extent than the rate of oxidation as sodium was replaced by potassium. In every preparation tested, the rates of phosphorylation and the P/O ratios were higher in the high-potassium media than in the high-sodium media.

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