Na+ absorption in Aplysia intestine: Na+ fluxes and intracellular Na+ and K+ activities

1983 ◽  
Vol 244 (3) ◽  
pp. R412-R417 ◽  
Author(s):  
G. A. Gerencser
Keyword(s):  
Ion Exchanger ◽  
Equilibrium Potential ◽  
Sodium Absorption ◽  
Bathing Solution ◽  
Mucosal Membrane ◽  
Intracellular Na Activity ◽  
Flux Measurements ◽  
Intracellular K Activity ◽  
Liquid Ion Exchanger ◽  
Electrochemical Equilibrium

Microelectrodes were used to measure the potential difference (psi m) across the mucosal membrane of epithelial cells lining the villi of isolated Aplysia californica intestine. In substrate-free NaCl seawater medium psi m was -55.1 +/- 1.2 mV. The cell interior was negative relative to the mucosal bathing solution. Intracellular K+ activity, determined in the absorptive cells with single-barreled liquid ion-exchanger microelectrodes, was 383 +/- 15 mM. Since the calculated K+ equilibrium potential exceeds the membrane potential, K+ is accumulated by the intestinal absorptive cell. Intracellular Na+ activity (aiNa) was also determined in the intestinal cells of Aplysia with single-barreled liquid ion-exchanger microelectrodes and was 17.2 +/- 2.5 mM. aiNa was much less than that predicted by the electrochemical equilibrium value for Na+ across the mucosal membrane. From these data the steady-state transapical Na+ and K+ electrochemical potential differences were calculated. Serosal ouabain abolished net sodium absorption as determined by flux measurements. These results are consistent with the operation of a basolateral Na+ - K+ pump.

Characteristics of basolateral Cl- transport by gastric surface epithelium in Necturus antral mucosa

1993 ◽  
Vol 264 (5) ◽  
pp. G910-G920 ◽  
Author(s):  
D. I. Soybel ◽  
M. B. Davis ◽  
L. Y. Cheung
Keyword(s):  
Nutrient Solution ◽  
Cell Membranes ◽  
Basolateral Membrane ◽  
Membrane Potentials ◽  
Gastric Antrum ◽  
Ion Exchanger ◽  
Surface Epithelium ◽  
Antral Mucosa ◽  
Liquid Ion Exchanger ◽  
Electrochemical Equilibrium

Conventional and ion-selective microelectrodes were used to characterize transport of Cl- across the basolateral cell membranes of gastric surface epithelium in isolated preparations of gastric antrum of Necturus. Conventional, voltage-sensing electrodes were used to evaluate changes in membrane potentials and resistances during removal of Cl- from the nutrient perfusate. Liquid ion exchanger Cl(-)-selective microelectrodes were constructed and validated to measure intracellular Cl- activity (aiCl). Our data indicate that 1) aiCl (range 12-25 mM) is close to that predicted if Cl- is distributed across the cell membranes by electrochemical equilibrium, 2) aiCl is not influenced by changes in luminal Cl- content but is susceptible to changes in nutrient Cl- content, 3) Cl- conductances cannot be detected in the basolateral membrane and changes in membrane potentials do not influence aiCl, and 4) Cl- accumulation across the basolateral membrane depends on Na+ and the level of [K+] in the nutrient solution. Inhibition of K(+)-dependent Cl- accumulation, in the absence of nutrient Na+ or in the presence of the inhibitor bumetanide, was demonstrated. These findings suggest that basolateral Na(+)-K(+)-Cl- cotransport is important in regulating cell Cl- levels in surface cells of the gastric antrum in Necturus.

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.

K activity of CCD principal cells from normal and DOCA-treated rabbits

1989 ◽  
Vol 256 (1) ◽  
pp. F136-F142 ◽  
Author(s):  
S. C. Sansom ◽  
S. Agulian ◽  
S. Muto ◽  
V. Illig ◽  
G. Giebisch
Keyword(s):  
Driving Forces ◽  
Basolateral Membrane ◽  
Cell Secretion ◽  
Principal Cells ◽  
K Secretion ◽  
Intracellular K Activity ◽  
K Transport ◽  
Liquid Ion Exchanger ◽  
Electrochemical Equilibrium ◽  
K Activity

We used liquid ion exchanger and conventional microelectrodes to evaluate the effects of mineralocorticoids on the intracellular K activity (aiK) and K transport properties of principal cells (PC) of isolated cortical collecting ducts (CCDs). Hoffman modulation optics and electrophysiological methods were used to identify PC. K activity was measured with two single-barreled electrodes. We found that aiK of PC from deoxycorticosterone acetate (DOCA)-treated rabbits (97.6 mM) was not different from controls (94.8 mM). The driving forces for K transport across the basolateral membrane favored cell to bath (reabsorption) in PCs from controls and bath to cell (secretion) in PCs from DOCA-treated rabbits. However, the driving force for K secretion across the apical membrane was not significantly different between the two groups. We used the intracellular aiKs and bath ion substitutions (gluconate for Cl and K for Na) to evaluate the effects of DOCA on the ion-selective properties of the basolateral membrane of PC. DOCA increased PK/PCl from 0.33 to 0.89. Our conclusion was as follows: in PC of control rabbits K is above electrochemical equilibrium across the basolateral membrane. However, the basolateral K conductance is probably too small for significant K recycling. In PC of DOCA-treated rabbits the aiK is below electrochemical equilibrium across the basolateral membrane and the K conductance is increased. These effects enhance K secretion across this border while maintaining cell K constant.

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.

scholarly journals Quantitative analysis of resting membrane electrogenesis in insect (diptera) skeletal muscle. I. Intracellular K+, Na+ and Cl- activities, measured using liquid ion-exchanger and neutral ion-carrier microelectrodes

1988 ◽  
Vol 136 (1) ◽  
pp. 417-432
Author(s):  
J. Dawson ◽  
M. B. Djamgoz
Keyword(s):  
Mean Value ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Calliphora Erythrocephala ◽  
Electrophysiological Properties ◽  
Intracellular Na Activity ◽  
Body Wall Muscles ◽  
Ion Sensitive Microelectrodes ◽  
The Mean ◽  
Intracellular K Activity

Electrophysiological properties of skeletal body-wall muscles of prepupal Calliphora erythrocephala were investigated using double-barrelled intracellular ion-sensitive microelectrodes. The most realistic estimate of the intracellular K+ activity, obtained using K+-sensitive microelectrodes based on a neutral carrier, was 115 mmoll-1. The K+ equilibrium potential was consistently more negative than the prevailing resting potential, the average difference being −15 mV. The intracellular Na+ activity and the Na+ equilibrium potential were 7 mmoll-1 and +46 mV on average, respectively. The mean value of the intracellular Cl- activity was 40 mmoll-1, and this was apparently higher than that required for passive distribution of Cl-. However, when reversibly exposed to a Ringer containing no Cl-, cells could rapidly exchange most of their intracellular Cl-, although the resting membrane potentials were only transiently affected. It is concluded that an anionic interferent exists inside muscles, that this artefactually elevates the measured intracellular Cl- activities, and that Cl- makes no contribution to resting membrane electrogenesis.

Submicron tip breakage and silanization control improve ion-selective microelectrodes

1985 ◽  
Vol 249 (5) ◽  
pp. C514-C521 ◽  
Author(s):  
S. Tripathi ◽  
N. Morgunov ◽  
E. L. Boulpaep
Keyword(s):  
Electromotive Force ◽  
Contact Angles ◽  
Ambystoma Tigrinum ◽  
Glass Wall ◽  
Solution Interface ◽  
Intracellular Na Activity ◽  
Electrode Resistance ◽  
The Mean ◽  
Liquid Ion Exchanger ◽  
Causes Of Failure

Probable causes of failure of otherwise well-constructed liquid ion-exchanger (LIE) micro-electrodes of average tip size less than 0.15 micron were examined. The problem could be attributed to two major variables, both localized at the tip: partial tip occlusion during fabrication prevents the generation of an electromotive force (small or absent slope and/or selectivity, high resistance); or poor hydrophobicity of the tip permits water to displace the resin from the tip (small or absent slope and/or selectivity and low electrode resistance). Controlled dry tip breakage on paper coated with glassine to final tip sizes well below 0.5 micron (confirmed by scanning electron microscopy) improves the yield of usable electrodes severalfold. Adequate silanization of the tip and consequent retention of resin at the tip can be predicted from the contact angles observed at the glass-LIE-backfilling solution interface. Satisfactory silanization can be achieved despite high ambient humidity. No evidence of shunting of Na+-LIE microelectrodes by the glass wall was seen. In the isolated perfused proximal tubule of Ambystoma tigrinum, the mean intracellular Na+ activity recorded by broken-tip electrodes (13.7 +/- 1.9 meq, n = 4) was similar to that recorded by intact electrodes (15.5 +/- 1.1 meq, n = 31).

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