Comprehensive Physiology Wiley Online Library

Distribution and exchange of electrolytes in gastrointestinal muscle cells

Full Article on Wiley Online Library



Abstract

The sections in this article are:

1 Ionic Content
1.1 Chemical Analysis
1.2 Tissue Tracer Content
1.3 Electron Microscopy and X‐Ray Microanalysis
1.4 Ion‐Sensitive Microelectrodes
1.5 Optical Methods
2 Ion Movements
2.1 Passive Ion Movements
2.2 Active Transport
2.3 Exchange Mechanism
Figure 1. Figure 1.

Frequency distribution of cytoplasmic Na+ concentrations measured by electron‐probe microanalysis in Na+‐loaded cells of guinea pig taenia coli and its changes by exposure for 30 min to cold Na+‐free, Li+‐containing solution. A: bimodal distribution in Na+‐loaded cells; B: frequency distribution in paired Na+‐loaded cells after 30‐min wash in Li+ solution.

From Junker et al. by permission of the American Heart Association, Inc.
Figure 2. Figure 2.

A: changes of intracellular Na+ concentrations ([Na+]i) induced by readmission of different external K+ concentrations ([K+]o) to tissues depleted of K+ by 4‐h exposure to K+‐free solution. [K+]o (mM): 1.2 (circle), 2.95 (square), 5.9 (triangle), 11.6 (inverted triangle), 23.6 (diamond). B: initial rate of change of (Na+]i was taken as measure of active Na+ extrusion and plotted as function of [K+]o C: these values, normalized with respect to maximum efflux rate and [K+] giving half‐maximal activation , are replotted with theoretical curves for first‐order (n = 1) and second‐order (n = 2) system. [A from Casteels et al. , B from Casteels et al. .]

Figure 3. Figure 3.

A: changes of membrane potential (closed circle) and of equilibrium potential of K+ () (open circle) of K+‐depleted taenia coli cells during K+ accumulation in Cl‐containing solution with 5.9 mM external K+ concentration. B: solution changed to one in which Cl−1 is replaced by proprionate. values calculated by Nernst equation from measured intracellular [K+].

From Casteels et al.
Figure 4. Figure 4.

Recording of the Na+‐K+‐ATPase and Ca2+‐Mg2+‐ATPase activity in plasma membrane fraction from pig antrum smooth muscle. With lactate dehydrogenase‐pyruvate kinase‐coupled enzyme system, oxidation of NADH was followed at 340 nm in double‐beam spectrophotometer. Curve 1 (control): medium contained ethylene glycol‐bis(β‐aminoethylether)‐N,N'‐tetraacetic acid (EGTA) without added Ca2+, and both cuvettes were of identical composition. Curve 2: 5 μM digitoxigenin added to sample cuvette. Difference in slope between curves 1 and 2 represents Na+‐K+‐ATPase activity. Curve 3: CaCl2 was added to reference cuvette to obtain 10−5 M Ca2+. Difference in slope between curve 2 and 3 represents Ca2+‐Mg2+‐ATPase activity. Curve 4: 100 μg/ml calmodulin added to stimulate Ca2+‐Mg2+‐ATPase activity. OD, optical density. Reaction conditions: NaCl, 100 mM; Imidazol‐HCl, 30 mM (pH 7.3); EGTA, 0.5 mM; Tris‐ATP, 5 mM; MgCl2, 6 mM; NaN3, 5 mM; phosphoenolpyruvate, 1.5 mM; NADH, 0.26 mM units/ml; temperature, 37°C; protein concentration, 20 μg/Ml.

Figure 5. Figure 5.

Subfractionation of digitonin‐treated membranes isolated from antral part of pig stomach on sucrose density gradient containing 0.6 M KCl. Sample was applied below 15%‐45% sucrose gradient in zonal rotor and centrifuged overnight at 105,000 gmax. A: density distributions of protein content, B‐D: marker enzyme activities, E: Ca2+ uptake, and F: 125I‐labeled calmodulin binding are shown. Solid lines and open symbols: control without digitonin. Broken lines and closed symbols: sample treated with digitonin. Plasma membrane markers 5'‐nucleotidase and Na+‐K+‐ATPase are shifted by digitonin to higher densities. Largest part of Ca2+‐Mg2+‐ATPase and oxalate‐independent Ca2+ uptake is shifted in parallel. Largest fraction of oxalate‐stimulated Ca2+ uptake and small fraction of Ca2+‐Mg2+‐ATPase activity remains at lower density. This fraction represents highly enriched endoplasmic reticulum.

From Raeymaeckers et al.
Figure 6. Figure 6.

Autoradiogram of dried polyacrylamide slab gel showing Ca2+‐dependent phosphorylated intermediates of Ca2+‐transport ATPases of subcellular fractions from pig stomach smooth muscle, separated by digitonin treatment (see Fig. legend). Fractions II‐IX were collected from gradient from low to high density. Fractions II‐IV are most enriched in endoplasmic reticulum, fractions VI‐VIII in plasma membranes. Phosphorylation was carried out in presence of 50 μM Ca2+ with (bottom) or without (top) 50 μM La3+. For comparison, inside‐out vesicles of pig erythrocyte membranes (ERY) and sarcoplasmic reticulum membranes from pig skeletal muscle (SR) were treated in parallel. Experiment clearly shows predominance of 130,000‐Mr erythrocyte‐type ATPase in plasma membrane fraction and 100,000‐Mr sarcoplasmic reticulum‐type ATPase in endoplasmic reticulum. Level of phosphorylation of 130,000‐Mr ATPase is increased by La3+, whereas that of 100,000‐M, ATPase is decreased.

From Raeymaeckers et al.
Figure 7. Figure 7.

Graph of Na+‐induced Ca2+ uptake (circle) and ATP‐dependent Ca2+ uptake (triangle) activities as function of free Ca2+ concentration in medium. Left: in intestinal smooth muscle microsomes. Right: in cardiac plasma membrane‐rich fraction. For experimental details see ref. 112.

From Morel and Godfraind
Figure 8. Figure 8.

Graph of 36Cl efflux from guinea pig vas deferens into Cl‐free solution expressed by fractional loss as function of time. Data obtained in presence of CO2 and (circles), in nominal absence of CO2 and (squares), and in presence of 130 μM 4,4'‐diisothiocyanostilbene‐2,2'‐disulfonic acid (DIDS) (triangles). CO2 added to or removed from wash out solution at 23 min after starting wash out (open symbols), no change in solution (closed symbols).

From Aickin and Brading
Figure 9. Figure 9.

Schematic of proposed combined activity of Na+‐H+ exchanger and exchanger in membrane of smooth muscle cell. Intracellular carbonic anhydrase (c.a.) accelerates formation of from OH and CO2. Inwardly directed Na+ gradient moves H+ out, creating outwardly directed OH or gradient that moves Cl inward through exchanger.



Figure 1.

Frequency distribution of cytoplasmic Na+ concentrations measured by electron‐probe microanalysis in Na+‐loaded cells of guinea pig taenia coli and its changes by exposure for 30 min to cold Na+‐free, Li+‐containing solution. A: bimodal distribution in Na+‐loaded cells; B: frequency distribution in paired Na+‐loaded cells after 30‐min wash in Li+ solution.

From Junker et al. by permission of the American Heart Association, Inc.


Figure 2.

A: changes of intracellular Na+ concentrations ([Na+]i) induced by readmission of different external K+ concentrations ([K+]o) to tissues depleted of K+ by 4‐h exposure to K+‐free solution. [K+]o (mM): 1.2 (circle), 2.95 (square), 5.9 (triangle), 11.6 (inverted triangle), 23.6 (diamond). B: initial rate of change of (Na+]i was taken as measure of active Na+ extrusion and plotted as function of [K+]o C: these values, normalized with respect to maximum efflux rate and [K+] giving half‐maximal activation , are replotted with theoretical curves for first‐order (n = 1) and second‐order (n = 2) system. [A from Casteels et al. , B from Casteels et al. .]



Figure 3.

A: changes of membrane potential (closed circle) and of equilibrium potential of K+ () (open circle) of K+‐depleted taenia coli cells during K+ accumulation in Cl‐containing solution with 5.9 mM external K+ concentration. B: solution changed to one in which Cl−1 is replaced by proprionate. values calculated by Nernst equation from measured intracellular [K+].

From Casteels et al.


Figure 4.

Recording of the Na+‐K+‐ATPase and Ca2+‐Mg2+‐ATPase activity in plasma membrane fraction from pig antrum smooth muscle. With lactate dehydrogenase‐pyruvate kinase‐coupled enzyme system, oxidation of NADH was followed at 340 nm in double‐beam spectrophotometer. Curve 1 (control): medium contained ethylene glycol‐bis(β‐aminoethylether)‐N,N'‐tetraacetic acid (EGTA) without added Ca2+, and both cuvettes were of identical composition. Curve 2: 5 μM digitoxigenin added to sample cuvette. Difference in slope between curves 1 and 2 represents Na+‐K+‐ATPase activity. Curve 3: CaCl2 was added to reference cuvette to obtain 10−5 M Ca2+. Difference in slope between curve 2 and 3 represents Ca2+‐Mg2+‐ATPase activity. Curve 4: 100 μg/ml calmodulin added to stimulate Ca2+‐Mg2+‐ATPase activity. OD, optical density. Reaction conditions: NaCl, 100 mM; Imidazol‐HCl, 30 mM (pH 7.3); EGTA, 0.5 mM; Tris‐ATP, 5 mM; MgCl2, 6 mM; NaN3, 5 mM; phosphoenolpyruvate, 1.5 mM; NADH, 0.26 mM units/ml; temperature, 37°C; protein concentration, 20 μg/Ml.



Figure 5.

Subfractionation of digitonin‐treated membranes isolated from antral part of pig stomach on sucrose density gradient containing 0.6 M KCl. Sample was applied below 15%‐45% sucrose gradient in zonal rotor and centrifuged overnight at 105,000 gmax. A: density distributions of protein content, B‐D: marker enzyme activities, E: Ca2+ uptake, and F: 125I‐labeled calmodulin binding are shown. Solid lines and open symbols: control without digitonin. Broken lines and closed symbols: sample treated with digitonin. Plasma membrane markers 5'‐nucleotidase and Na+‐K+‐ATPase are shifted by digitonin to higher densities. Largest part of Ca2+‐Mg2+‐ATPase and oxalate‐independent Ca2+ uptake is shifted in parallel. Largest fraction of oxalate‐stimulated Ca2+ uptake and small fraction of Ca2+‐Mg2+‐ATPase activity remains at lower density. This fraction represents highly enriched endoplasmic reticulum.

From Raeymaeckers et al.


Figure 6.

Autoradiogram of dried polyacrylamide slab gel showing Ca2+‐dependent phosphorylated intermediates of Ca2+‐transport ATPases of subcellular fractions from pig stomach smooth muscle, separated by digitonin treatment (see Fig. legend). Fractions II‐IX were collected from gradient from low to high density. Fractions II‐IV are most enriched in endoplasmic reticulum, fractions VI‐VIII in plasma membranes. Phosphorylation was carried out in presence of 50 μM Ca2+ with (bottom) or without (top) 50 μM La3+. For comparison, inside‐out vesicles of pig erythrocyte membranes (ERY) and sarcoplasmic reticulum membranes from pig skeletal muscle (SR) were treated in parallel. Experiment clearly shows predominance of 130,000‐Mr erythrocyte‐type ATPase in plasma membrane fraction and 100,000‐Mr sarcoplasmic reticulum‐type ATPase in endoplasmic reticulum. Level of phosphorylation of 130,000‐Mr ATPase is increased by La3+, whereas that of 100,000‐M, ATPase is decreased.

From Raeymaeckers et al.


Figure 7.

Graph of Na+‐induced Ca2+ uptake (circle) and ATP‐dependent Ca2+ uptake (triangle) activities as function of free Ca2+ concentration in medium. Left: in intestinal smooth muscle microsomes. Right: in cardiac plasma membrane‐rich fraction. For experimental details see ref. 112.

From Morel and Godfraind


Figure 8.

Graph of 36Cl efflux from guinea pig vas deferens into Cl‐free solution expressed by fractional loss as function of time. Data obtained in presence of CO2 and (circles), in nominal absence of CO2 and (squares), and in presence of 130 μM 4,4'‐diisothiocyanostilbene‐2,2'‐disulfonic acid (DIDS) (triangles). CO2 added to or removed from wash out solution at 23 min after starting wash out (open symbols), no change in solution (closed symbols).

From Aickin and Brading


Figure 9.

Schematic of proposed combined activity of Na+‐H+ exchanger and exchanger in membrane of smooth muscle cell. Intracellular carbonic anhydrase (c.a.) accelerates formation of from OH and CO2. Inwardly directed Na+ gradient moves H+ out, creating outwardly directed OH or gradient that moves Cl inward through exchanger.

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R. Casteels, G. Droogmans, L. Raeymaekers. Distribution and exchange of electrolytes in gastrointestinal muscle cells. Compr Physiol 2011, Supplement 16: Handbook of Physiology, The Gastrointestinal System, Motility and Circulation: 141-162. First published in print 1989. doi: 10.1002/cphy.cp060103