Measurements of the Intracellular Potassium Activity of Retzius Cells in the Leech Central Nervous System

1981 ◽  
Vol 91 (1) ◽  
pp. 87-101
Author(s):  
JOACHIM W. DEITMER ◽  
WOLF R. SCHLUE
Keyword(s):  
Cell Membrane ◽  
External Solution ◽  
Equilibrium Potential ◽  
The Mean ◽  
K Concentration ◽  
Retzius Cells ◽  
Intracellular K Activity ◽  
K Permeability ◽  
K Activity ◽  
External K

The intracellular K activity of leech Retzius cells was measured using double-barrelled, liquid ion exchanger, microelectrodes. At the normal external K+ concentration of 4 mm (equivalent to 3 mm-K activity, assuming an activity coefficient of 0.75) the mean K activity was 101.3 ± 7.6 mm (S.D., n = 14) in the cell bodies, and 4.35 ± 0.4 mV (n = 27) in the extracellular spaces surrounding them, indicating a K+ equilibrium potential of - 80 mV. The mean membrane potential was - 43.6 + 4.9 mV (n = 14). In a K-free external solution, or in the presence of 5 × 10−4m-ouabain, the intracellular K activity decreased by up to 14 mm min−1. This indicates an efflux of K+ ions across the cell membrane of approximately 2 × 10−10 mol cm−2s, and an apparent K+ permeability coefficient of 8 × 10−8 cms−1. The cell membrane depolarized upon removal of K+ and upon addition of ouabain, and transiently hyperpolarized beyond its initial level on return to the normal external K+ concentration. The recovery from this hyperpolarization paralleled the increase of the intracellular K activity following the re-addition of K+. Our results suggest that, despite the high K+ permeability of the Retzius cell membrane, the intracellular K activity is maintained at a high level by an electrogenic pump.

Potassium distribution and membrane potential of sensory neurons in the leech nervous system

1984 ◽  
Vol 51 (4) ◽  
pp. 689-704 ◽  
Author(s):  
W. R. Schlue ◽  
J. W. Deitmer
Keyword(s):  
Nervous System ◽  
Membrane Potential ◽  
Sensory Neurons ◽  
Membrane Resistance ◽  
Equilibrium Potential ◽  
Bathing Medium ◽  
Membrane Hyperpolarization ◽  
K Concentration ◽  
Intracellular K Activity ◽  
K Activity

The intracellular K activity (aKi) and membrane potential of sensory neurons in the leech central nervous system were measured in normal and altered external K+ concentrations, [K+]o, using double-barreled, liquid ion-exchanger microelectrodes. In control experiments membrane potential measurements were made using potassium chloride-filled single-barreled microelectrodes. All values are means +/- SD. At the normal [K+]o (4 mM) the mean aKi of all cells tested was 72.6 +/- 10.6 mM (n = 40) and the average membrane potential was -47.3 +/- 5.2 mM (n = 40). When measured with single-barreled microelectrodes, the membrane potential averaged -45.3 +/- 2.9 mV (n = 12). Assuming an intracellular K+ activity coefficient of 0.75, the intracellular K+ concentration of sensory neurons would be 96.8 +/- 14.1 mM). With an extracellular K+ concentration of 5.8 mM in the intact ganglion compared to the K+ concentration of 4 mM in the bath, the K+ equilibrium potential was -71.5 mV. When the ganglion capsule was opened, the extracellular K+ concentrations in the ganglion were similar to that of the bathing medium and the calculated K+ equilibrium potential was -81 mV. The membrane of sensory neurons depolarized following the changes to elevated [K+]o (greater than or equal to 10-100 mM), whereas aKi changed only little or not at all. At very low [K+]o (0.2, 0 mM) aKi and membrane potential showed little short-term (less than 3 min) effect but began to change after longer exposure (greater than 3 min). Reduction of [K+]o from 4 to 0.2 mM (or 0 mM) produced first a slow, and then a more rapid decrease of aKi and membrane resistance, accompanied by a slow membrane hyperpolarization. Following readdition of normal [K+]o, the membrane first depolarized and then transiently hyperpolarized, eventually returning slowly to the normal membrane potential.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals The effect of extracellular potassium on the intracellular potassium ion activity and transmembrane potentials of beating canine cardiac Purkinje fibers.

1977 ◽  
Vol 69 (4) ◽  
pp. 463-474 ◽  
Author(s):  
D S Miura ◽  
B F Hoffman ◽  
M R Rosen
Keyword(s):  
Equilibrium Potential ◽  
Extracellular Potassium ◽  
Purkinje Fibers ◽  
Transmembrane Potentials ◽  
Cardiac Purkinje Fibers ◽  
K Concentration ◽  
Range Of Values ◽  
Intracellular K Activity ◽  
Liquid Ion Exchanger ◽  
K Activity

We used open tip microelectrodes containing a K+-sensitive liquid ion exchanger to determine directly the intracellular K+ activity in beating canine cardiac Purkinje fibers. For preparations superfused with Tyrode's solution in which the K+ concentration was 4.0 mM, intracellular K+ activity (ak) was 130.0+/-2.3 mM (mean+/-SE) at 37 degrees C. The calculated K+ equilibrium potential (EK) was -100.6+/-0.5 mV. Maximum diastolic potential (ED) and resting transmembrane potential (EM) were measured with conventional microelectrodes filled with 3 M KCl and were -90.6+/-0.3 and -84.4+/-0.4 mV, respectively. When [K+]o was decreased to 2.0 mM or increased to 6.0, 10.0, and 16.0 mM, ak remained the same. At [K+]o=2.0, ED was -97.3+/-0.4 and Em -86.0+/-0.7 mV; at [K+]o=16.0, ED fell to -53.8+/-0.4 mV and Em to the same value. Over this range of values for [K+]o, EK changed from -119.0+/-0.3 to -63.6+/-0.2 mV. These values for EK are consistent with those previously estimated indirectly by other techniques.

scholarly journals Intracellular K+ activity and its relation to basolateral membrane ion transport in Necturus gallbladder epithelium.

1980 ◽  
Vol 76 (1) ◽  
pp. 33-52 ◽  
Author(s):  
L Reuss ◽  
S A Weinman ◽  
T P Grady
Keyword(s):  
Cell Membrane ◽  
Amphotericin B ◽  
Basolateral Membrane ◽  
Membrane Potentials ◽  
Equilibrium Potential ◽  
Gallbladder Epithelium ◽  
Bathing Medium ◽  
Necturus Gallbladder ◽  
Intracellular K Activity ◽  
K Activity

A study of the mechanisms of the effects of amphotericin B and ouabain on cell membrane and transepithelial potentials and intracellular K activity (alpha Ki) of Necturus gallbladder epithelium was undertaken with conventional and K-selective intracellular microelectrode techniques. Amphotericin B produced a mucosa-negative change of transepithelial potential (Vms) and depolarization of both apical and basolateral membranes. Rapid fall of alpha Ki was also observed, with the consequent reduction of the K equilibrium potential (EK) across both the apical and the basolateral membrane. It was also shown that, unless the mucosal bathing medium is rapidly exchanged, K accumulates in the unstirred fluid layers near the luminal membrane generating a paracellular K diffusion potential, which contributes to the Vms change. Exposure to ouabain resulted in a slow decrease of alpha Ki and slow depolarization of both cell membranes. Cell membrane potentials and alpha Ki could be partially restored by a brief (3-4 min) mucosal substitution of K for Na. Under all experimental conditions (control, amphotericin B, and ouabain), EK at the basolateral membrane was larger than the basolateral membrane equivalent emf (Eb). Therefore, the K chemical potential difference appears to account for Eb and the magnitude of the cell membrane potentials, without the need to postulate an electrogenic Na pump. Comparison of the rate of Na transport across the tissue with the electrodiffusional K flux across the basolateral membrane indicates that maintenance of a steady-state alpha Ki cannot be explained by a simple Na,K pump-K leak model. It is suggested that either a NaCl pump operates in parallel with the Na,K pump, or that a KCl downhill neutral extrusion mechanism exists in addition to the electrodiffusional K pathway.

Mechanism of potassium uptake in neuropile glial cells in the central nervous system of the leech

1990 ◽  
Vol 63 (5) ◽  
pp. 1089-1097 ◽  
Author(s):  
W. A. Wuttke
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Cell Volume ◽  
Normal Saline ◽  
Cell Swelling ◽  
Equilibrium Potential ◽  
K Uptake ◽  
The Central Nervous System ◽  
The Mean ◽  
K Concentration

1. Ion-selective double-barreled microelectrodes (ISME) were used to measure intracellular K+ (aKi), Na+ (aNai), and Cl- (aCli) activities of neuropile glial (NG) cells in the central nervous system of the medicinal leech Hirudo medicinalis. Ion fluxes were induced by an increase in extracellular K+ concentration [( K+]o) and analyzed to elucidate the ionic mechanism of the K+ uptake occurring under such conditions. 2. In addition, the K+ concentration of the extracellular space of the nerve cell body region (NCBR) and the neuropile (N) was measured with neutral carrier K(+)-ISME. In normal saline (4 mM K+), a concentration of 4.2 mM was measured in both extracellular spaces. No differences between the K+ concentration of the bathing fluid and the extracellular spaces were found at higher (i.e., 10 and 40 mM) K+ concentrations. 3. In normal saline, the mean membrane potential (Em) was -68 mV, and the mean aKi, aNai, and aCli were found to be 77, 10, and 7 mM, respectively. The corresponding equilibrium potentials were -81, 56, and -66 mV. The chloride equilibrium potential (ECl) was similar to Em, and it is concluded that chloride is passively distributed across the NG cell membrane. 4. When [K+]o was transiently increased 10-fold (i.e., to 40 mM), aKi and a Cli increased transiently by 22 and 25 mM, respectively, and the membrane depolarized to -28 mV, which was similar to both K+ equilibrium potential (EK) and ECl. The KCl uptake was accompanied by a transient decrease in aNai to 5 mM. 5. After incubation for at least 1 h in Na(+)-free saline, NG cells accumulated K+ in the absence of extracellular Na+ to levels similar to those observed in the presence of Na+. Therefore the uptake of K+ was not dependent on external--and probably also internal--Na+. 6. Changes in cell volume induced by the increase in [K+]o were estimated by loading NG cells with choline and monitoring its intracellular concentration with Corning-K(+)-ISME. In saline containing 40 mM K+, NG cell volume increased to approximately 150% of its volume in normal saline. 7. It is concluded that the mechanism of K+ uptake in NG cells is by passive KCl and water influx, which causes cell swelling.

The diffusion and electrogenic components of the membrane potential of hypoxic myocardium

1987 ◽  
Vol 65 (2) ◽  
pp. 246-251 ◽  
Author(s):  
Normand Leblanc ◽  
Elena Ruiz-Ceretti
Keyword(s):  
Membrane Potential ◽  
Sodium Pump ◽  
Resting Potential ◽  
Krebs Solution ◽  
Ventricular Muscle ◽  
Diffusion Component ◽  
K Concentration ◽  
Zero Potential ◽  
K Permeability ◽  
External K

The diffusion and electrogenic components of the resting potential of hypoxic ventricular muscle were separated by inhibition of the sodium pump with 10−4 M ouabain. The response to varying external K concentrations (Ko) was studied. Arteriaily perfused rabbit hearts were submitted to 60 min hypoxia in Krebs solution containing 5 mM K throughout or to different external K concentrations during the last 20 min of hypoxia. For K concentrations between 1.5 and 10 mM, hypoxia did not change the resting potential except for a slight hyperpolarization in 7.5 mM K. The diffusion component of the resting potential did not differ from the resting potential at Ko < 5 mM. An electrogenic potential of −3 to −6 mV was detectable at Ko values between 5 and 10 mM. The internal K concentration, Ki, was estimated from extrapolations to zero potential of the relation resting potential vs. Ko in normoxic and hypoxic hearts. These experiments revealed a decline of Ki of 16 mM with hypoxia. The variation of the diffusion potential with external K was fitted by a PNa:PK ratio five times lower than in normoxia. It has been concluded that an increase in K permeability and the persistence of electrogenic Na extrusion during hypoxia of rather short duration prevent membrane depolarization despite the myocardial K loss.

scholarly journals Cat Heart Muscle in Vitro

1962 ◽  
Vol 46 (2) ◽  
pp. 189-199 ◽  
Author(s):  
Ernest Page
Keyword(s):  
Steady State ◽  
Heart Muscle ◽  
Potential Difference ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Papillary Muscles ◽  
K Concentration ◽  
Cat Heart ◽  
External K

The steady state transmembrane resting potential difference (Vm) has been measured in quiescent papillary muscles. Vm was determined as a function of the external K concentration in Cl and SO4 solutions and compared with the K equilibrium potential. Other measurements were made after replacement of external Na by choline, K by Rb and Cs, and Cl by SO4, CH3SO4, and NO3. Effects on Vm of albumin, temperature, and variation in internal K concentration are described.

scholarly journals Activities of potassium and sodium ions in rabbit heart muscle.

1975 ◽  
Vol 65 (6) ◽  
pp. 695-708 ◽  
Author(s):  
C O Lee ◽  
H A Fozzard
Keyword(s):  
Ionic Strength ◽  
Cell Membrane ◽  
Activity Coefficient ◽  
Heart Muscle ◽  
Extracellular Fluid ◽  
Rabbit Heart ◽  
Mean Value ◽  
Sodium Ions ◽  
K Activity ◽  
External K

Activities (a) of intracellular K and Na in rabbit ventricular papillary muslces were determined with cation-selectivve glass microelectrodes and concentrations (C) were estimated with flame photometry. The CK and aK of the muscles were 134.9 +/- 3.1 mM (mean value +/- SE) and 82.6 mM, respectively, at 25 degrees C. The corresponding CNa and aNa were 32.7 +/- 2.7 and 5.7, respectively. The apparent intracellular activity coefficients for K (gammaK) and Na (gammaNa) were 0.612 and 0.175, respectively. Similar results were obtained at 35 +/- 1 degree C. gammaK was substantially lower than the activity coefficient (0.745) of extracellular fluid (Tyrode's solution), which might be expected on the basis of a different intracellular ionic strength. gammaNa was much lower than that of extracellular fluid, and suggest that much of the Na was compartmentalized or sequestered. For external K concentrations greater than 5 mM, the resting membrane potentials agreed well with the potential differences calculated from the K activity gradients across the cell membrane as a potassium electrode. These results emphasize that potassium equilibrium potentials in heart muscle should be calculated by activities rather than concentrations.

Effect of sugars and amino acids on amphibian intestinal Cl- transport and intracellular Na+, K+, and Cl- activity

1986 ◽  
Vol 250 (1) ◽  
pp. G109-G117
Author(s):  
J. F. White ◽  
K. Burnup ◽  
D. Ellingsen
Keyword(s):  
Cellular Level ◽  
Equilibrium Potential ◽  
Cl Transport ◽  
Luminal Membrane ◽  
Intracellular Na Activity ◽  
The Difference ◽  
Effect Of Glucose ◽  
Intracellular K Activity ◽  
Intestinal Ion Transport ◽  
K Activity

The effect of glucose, galactose, and valine on intestinal Cl- transport and intracellular Cl-, Na+, and K+ activity was investigated in isolated segments of Amphiuma small intestine. By use of double-barreled Cl- -specific microelectrodes, it was observed that galactose and valine reduced the luminal membrane potential (psi m) and eliminated the difference between the Cl- equilibrium potential (ECl) and psi m, i.e., the Cl- accumulation potential (ECl-psi m) approached zero. Simultaneously, Cl- absorption (JnetCl) was reduced in short-circuited tissues and Na+ absorption was enhanced. In contrast, after exposure to glucose, psi m and ECl-psi m declined only transiently and JnetCl was unaltered. In tissues pretreated with galactose to reduce Cl- transport, addition of glucose to the serosal medium restored Cl- accumulation across the luminal membrane and the Cl- absorptive current. Glucose, galactose, and valine each reduced intracellular K+ activity significantly. Galactose and valine each increased [corrected] intracellular Na activity (aiNa) markedly, whereas glucose increased aiNa only slightly. In conclusion, intestinal ion transport can be limited by the availability of metabolic substrate. The nonmetabolized solutes galactose and valine inhibited Cl- uptake and net Cl- absorption while stimulating net Na absorption, as though net Na+ absorption has priority over Cl- transport at the cellular level. Cl- transport is reduced at both mucosal and serosal membranes. At the luminal membrane electrogenic Cl- uptake is slowed or a backleak of Cl- is enhanced; at the serosal membrane Cl- exchange with Na+ (and HCO3-) driven by the Na+ gradient is reduced. The availability of metabolizable glucose to the cell prevents the reduction in net Cl- absorption.

The α-action of catecholamines on the guinea-pig taenia coli in K-free and Na-free solution and in the presence of ouabain

1977 ◽  
Vol 197 (1128) ◽  
pp. 255-269 ◽  
Keyword(s):  
Guinea Pig ◽  
Prolonged Exposure ◽  
Membrane Conductance ◽  
Membrane Resistance ◽  
Equilibrium Potential ◽  
Taenia Coli ◽  
Free Solution ◽  
Na Pump ◽  
K Concentration ◽  
External K

The responses of guinea-pig taenia coli to the α-action of adrenaline and noradrenaline, recorded with the double sucrose-gap method, were ( a ) studied in conditions which inhibit Na-pump activity (exposure to 0 K, 0 Na, ouabain, low temperature) and ( b ) compared with the effect of Na-pump activation (readmission of K after prolonged exposure to 0 K). When the external K concentration was modified, the alteration of the change in membrane potential produced by the catecholamines was as would be expected from the shift of the K-equilibrium potential. The decrease in the membrane resistance was greater in a high external K con­centration and smaller in K-free solution. Readmission of K after prolonged exposure to K-free solution produced a large hyperpolarization, but, in the presence of ouabain (5 × 10 -5 M) or in the absence of Na, K readmission produced depolarization. In contrast, the effects of adrenaline and noradrenaline were not essentially modified by ouabain, nor by removal of Na. Reduction of the external K concentration enhanced the hyperpolarization by catecholamines even in the presence of ouabain or in the absence of external Na. During prolonged exposure to adrenaline or noradrenaline (7min) the increase in membrane conductance and the hyperpolarization of the membrane were largely maintained, though there was some spontaneous recovery in the presence of the catecholamines. These long-lasting respon­ses were essentially the same when the temperature was lowered from 37 to 20°C, and also in the presence of ouabain. All the results obtained were unaffected by the presence or absence of propranolol. It was concluded that the hyperpolarization produced by the α-action of catecholamines did not involve an activation of the Na-pump but was mainly caused by an increase in the K conductance of the membrane.

Interaction between carbachol and vasoactive intestinal peptide in cells of isolated colonic crypts

1992 ◽  
Vol 262 (5) ◽  
pp. G940-G944
Author(s):  
L. Greenwald ◽  
B. A. Biagi
Keyword(s):  
Vasoactive Intestinal Peptide ◽  
Chloride Transport ◽  
Basolateral Membrane ◽  
Distal Colon ◽  
Equilibrium Potential ◽  
Colonic Crypts ◽  
Intracellular K Activity ◽  
Crypt Cells ◽  
Basolateral Membrane Potential ◽  
K Activity

In a previous study [B. Biagi, Y.-Z. Wang, and H. J. Cooke, Am. J. Physiol. 258 (Gastrointest. Liver Physiol. 21): G223-G230, 1990], carbachol stimulated active chloride transport in rabbit distal colon, yet had no effect on the basolateral membrane potential (Vbl) of cells from isolated crypts from the same tissue. In the present study, crypt cells were first depolarized with vasoactive intestinal peptide (VIP; 1 x 10(-9) M) (control Vbl = -62 mV; VIP Vbl = -48 mV) and then exposed to carbachol in the presence of VIP. The VIP-induced depolarization of Vbl was completely reversed by carbachol (0.1 mM; repolarization to -65 mV). Similar repolarization was seen by applying carbachol to crypt cells depolarized by 10 mM aminophylline. Intracellular K+ activity (aiK), measured with K(+)-selective microelectrodes, was 64.3 mM (concn = 85 mM), yielding a K+ equilibrium potential (EK+) of -76 mV. Neither carbachol nor VIP application caused significant changes in aiK. These results demonstrate the presence of cholinergic receptors on colonic crypt cells. The magnitude of the carbachol effect on Vbl is greater when Vbl is depolarized relative to EK+. The results are consistent with the hypothesis that carbachol acts by increasing basolateral K+ conductance, driving the cell toward the EK+.

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