Segmental differences in electrical properties and Na-transport of rabbit caecum, proximal and distal colon in vitro

1985 ◽  
Vol 403 (3) ◽  
pp. 278-282 ◽  
Author(s):  
Wolfgang Clauss ◽  
Horst Sch�fer ◽  
Ingrid Horch ◽  
Heiko H�rnicke
Keyword(s):  
Electrical Properties ◽  
Distal Colon ◽  
Na Transport

Suppression of coupled Na-Cl absorption by aldosterone and dexamethasone in rat distal colon in vitro

1984 ◽  
Vol 246 (6) ◽  
pp. F785-F793 ◽  
Author(s):  
R. D. Perrone ◽  
S. L. Jenks
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Rat Colon ◽  
Na Transport ◽  
Unidirectional Flux ◽  
Rat Distal Colon ◽  
Marked Suppression ◽  
Stimulation Of

Basal Na absorption in the rat colon is coupled to that of Cl in an electroneutral fashion. We previously determined that aldosterone or dexamethasone induces amiloride-sensitive mucosal-to-serosal Na flux approximately equal to the amiloride-sensitive short-circuit current in rat distal colon in vitro. However, the effect of these steroids on coupled Na-Cl absorption was not examined. For this purpose, we determined the unidirectional flux of Na and Cl in voltage-clamped distal colon segments from rats treated with aldosterone or dexamethasone. Amiloride was used as a probe for conductive Na absorption, and acetazolamide and Cl-free solutions were used as probes for coupled Na-Cl absorption. Our results indicate that the nature of colonic Na absorption is markedly changed after treatment with these steroids. In contrast to findings in the untreated rat, colonic Na absorption after treatment with aldosterone or dexamethasone was largely independent of the presence of Cl. Net Cl absorption and acetazolamide sensitivity were both greatly diminished. Thus, aldosterone and dexamethasone have multiple effects on Na transport in rat distal colon. In addition to the stimulation of conductive Na absorption by aldosterone, an effect well described in other epithelia, there is marked suppression of coupled Na-Cl absorption. Dexamethasone was less effective in suppressing Cl absorption but equally effective in stimulating conductive Na absorption. These steroid effects were greater in the terminal 1-2 cm of the rat colon.

Characterization of conductive pathways in guinea pig distal colon in vitro

1985 ◽  
Vol 248 (2) ◽  
pp. G176-G183 ◽  
Author(s):  
W. Clauss ◽  
J. Durr ◽  
G. Rechkemmer
Keyword(s):  
Guinea Pig ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Na Transport ◽  
Cl Transport ◽  
Intracellular Na Activity ◽  
In Vitro Investigation ◽  
The Individual

Isolated mucosal sheets of guinea pig distal colon were studied in vitro in Ussing-type chambers, using a computer-controlled voltage clamp. A conductance of 8–12 mS/cm2 and spontaneous variations of the potential difference (Vt, -4 to +6 mV) and the short-circuit current (Isc, -1.6 to +1.5 mu eq X cm-2 X h-1) were observed. With use of a green feed diet these variations could be entirely attributed to the rate of Na transport. Unidirectional Na and Cl fluxes were measured, and for Na, K, and Cl transport the individual conductances and directions were estimated from the changes in Vt and Isc, using the appropriate blockers amiloride, barium, and piretanide. The sum of the electrogenic Na, K, and Cl transport determines the spontaneous electrical behavior of this epithelium. Na transport was further characterized with transepithelial and transapical current-voltage relations. Apical Na entry occurred by diffusion, intracellular Na activity was 12 mM, and apical Na permeability was calculated as 0.02 cm/h. This study represents the first in vitro investigation of electrogenic transport in this epithelium and shows that it closely resembles transport mechanisms found in rabbit colon.

Differential effects of corticosteroids on Na+ transport in rat distal colon in vitro

1985 ◽  
Vol 248 (4) ◽  
pp. G424-G431 ◽  
Author(s):  
D. Jorkasky ◽  
M. Cox ◽  
G. M. Feldman
Keyword(s):  
Short Circuit ◽  
Latency Period ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Molar Ratio ◽  
Na Transport ◽  
Cellular Mechanisms ◽  
Rat Distal Colon ◽  
Transport Control

We studied rat distal colon during in vitro incubation with aldosterone and dexamethasone. Both hormones caused short-circuit current (Isc) to increase with a latency period of approximately 3 h. At the 7th h of incubation, control colons had a Isc of 72 +/- 8 microA . cm-2 while tissues incubated with 10(-5) M aldosterone and 10(-8) M dexamethasone, the respective maximal stimulatory concentrations, had similarly increased Isc, 211 +/- 21 and 185 +/- 18 microA . cm-2, respectively. The increase in Isc induced by steroids reflected increased net sodium transport: control, 3.4 +/- 0.8; aldosterone, 6.7 +/- 0.7 (P less than 0.05); and dexamethasone, 7.5 +/- 1.0 mueq . h-1 . cm-2 (P less than 0.025). Spironolactone inhibited the response to both steroids, but the molar ratio of antagonist to agonist was less for aldosterone (approximately 5,000:1) than for dexamethasone (approximately 50,000:1). Amiloride inhibited a greater fraction of aldosterone-induced Isc (0.70 +/- 0.07) than that of dexamethasone (0.37 +/- 0.07; P less than 0.025). The latter value was similar to the effect of amiloride on control tissues (0.35 +/- 0.04). These data provide evidence that the cellular mechanisms by which aldosterone and dexamethasone induce Na+ transport are different.

Effects of aldosterone and dexamethasone on apical membrane properties and Na-transport of rabbit distal colon in vitro

1985 ◽  
Vol 403 (2) ◽  
pp. 186-192 ◽  
Author(s):  
Wolfgang Clauss ◽  
Johanna D�rr ◽  
Erik Skadhauge ◽  
Heiko H�rnicke
Keyword(s):  
Apical Membrane ◽  
Distal Colon ◽  
Membrane Properties ◽  
Na Transport

Synthesis, characterization, electrical properties, and Na+ transport pathways simulation in Na2ZnP1.5As0.5O7

Ionics ◽  
2021 ◽  
Author(s):  
Yossra Sallemi ◽  
Riadh Marzouki ◽  
Youssef Ben Smida ◽  
Adel A. El-zahhar ◽  
Mohsen Graia
Keyword(s):  
Electrical Properties ◽  
Na Transport ◽  
Transport Pathways

Postnatal development of colonic electrolyte transport in rabbits

1990 ◽  
Vol 258 (3) ◽  
pp. G447-G453 ◽  
Author(s):  
E. V. O'Loughlin ◽  
D. M. Hunt ◽  
D. Kreutzmann
Keyword(s):  
Chloride Transport ◽  
Age Groups ◽  
Serum Cortisol ◽  
Distal Colon ◽  
Proximal Colon ◽  
Transport Studies ◽  
Age Related ◽  
Serum Aldosterone ◽  
Group Transport

Postnatal changes in adrenal gluco- and mineralocorticoid secretion and colonic sodium and chloride transport were examined. New Zealand White rabbits, age 10-14, 18-22, and 25-30 days, and adult animals (6-10 wk) were studied. Serum cortisol, corticosterone, aldosterone, and mucosal Na(+)-K(+)-ATPase activities were measured in each age group. Transport studies were performed in vitro under short-circuited conditions in distal colon at all age groups and in proximal colon in days 10-14 and 18-22 and in adult animals. Serum glucocorticoids varied little until after day 30 when they rose to adult levels. On the other hand, serum aldosterone levels were two- to threefold higher in days 10-14 and 18-22 animals but fell to adult levels by day 25. In distal colon, amiloride-inhibitable electrogenic Na+ absorption was present at all ages but was significantly greater (P less than 0.01) in days 10-14 (3.8 +/- 0.5 mu eq.cm-2.h-1) and 18-22 (4.2 +/- 0.4) rabbits compared with adults (1.9 +/- 0.4) but not day 25-30 (2.8 +/- 0.5). In proximal colon, Na+ absorption was significantly higher (P less than 0.05) in day 10-14 (1.6 +/- 0.5 mu eq.cm-2.h-1) compared with day 18-22 (-0.2 +/- 0.5) and adults (0.06 +/- 0.5) and was amiloride insensitive. Neither chloride transport nor mucosal Na(+)-K(+)-ATPase demonstrated significant age-related changes in either region of colon. These results indicate that both proximal and distal colonic Na+ transport undergoes postnatal changes. In distal but not proximal colon these changes appear to be regulated by circulating aldosterone probably by increasing apical membrane permeability to Na+.

Bicarbonate secretion in rat distal colon in vitro: a measurement technique

1988 ◽  
Vol 254 (3) ◽  
pp. C383-C390 ◽  
Author(s):  
G. M. Feldman ◽  
S. F. Berman ◽  
R. L. Stephenson
Keyword(s):  
Short Circuit ◽  
Distal Colon ◽  
Apparent Permeability ◽  
Chemical Gradients ◽  
Acid Generation ◽  
Rat Distal Colon ◽  
Tissue Surfaces ◽  
Apparent Permeability Coefficient ◽  
Transepithelial Voltage

To study HCO3- secretion in rat distal colon, we utilized a technique that permits control of electrical and chemical transepithelial gradients. With symmetrical solutions (pH 7.4, [HCO3-] 25 mM, and CO2 tension 40 mmHg) bathing both tissue surfaces and under short-circuit conditions, HCO3- secretion remained stable for greater than 4 h at 1 mueq. h-1.cm-2. As the mucosal solution was alkalinized, the serosal solution was acidified at 3.1 mueq.h-1.cm-2. Ninety-four percent of serosal acidification was accounted for by the rate of metabolic lactic acid generation and transepithelial HCO3- secretion. Clamping transepithelial voltage reversibly affected net HCO3- secretion, and a linear relationship existed between clamped mucosal voltage and net HCO3- flux (r = 0.99); mucosal voltage of -68 mV completely inhibited net secretion. The apparent permeability coefficient of the colon to HCO3- is 2.8 X 10(-6) cm/s. One millimolar ouabain completely inhibited net HCO3- secretion. Acetazolamide (10(-4) M) inhibited secretion by approximately 50%, whereas a 10(-3) M concentration inhibited secretion by 90%. These data demonstrate that net colonic HCO3- secretion can be measured without imposed electrical and chemical gradients and that this flux is voltage sensitive and depends on carbonic anhydrase and Na+-K+-ATPase activities.

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