Ba++ on the resting frog stomach: effects on electrical and secretory parameters

1975 ◽  
Vol 228 (2) ◽  
pp. 511-517 ◽  
Author(s):  
PK Rangachari
Keyword(s):  
Acid Secretion ◽  
Nutrient Solution ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Secretory Rate ◽  
Frog Stomach ◽  
Solution Bathing ◽  
Per Se

Ba++ added to the nutrient solution bathing the resting frog stomach increased resistance, decreased the PD, and stimulated acid secretion. Under short-circuit conditions, the increase in H+-secretory rate was accompanied by a decrease in short-circuit current (I-sc). These changes were reversed by NaSCN (10 mM), suggesting that Ba++ had not impaired the current-generating mechanism per se. Histamine-induced acid secretion was associated with an increase in net Cl- flux, particularly in the N yields S flux (JNS). Ba++ increased acid secretion with no increase in JNS and a decrease in net Cl- flux. The effects of Ba++ were amplified by low-Cl- solutions. Histamine, in the presence of Ba++ and low-Cl- solutions, increased acid secretion and transmucosal resistance, suggesting the operation of a neutral pump in the secretion of HCl. It is concluded that Ba++ limits Cl- entry and also acts as a secretagogue.

Electrophysiology of the frog gastric mucosa with sufficient CO2

1975 ◽  
Vol 228 (3) ◽  
pp. 928-933 ◽  
Author(s):  
Kidder GW
Keyword(s):  
Gastric Mucosa ◽  
Acid Secretion ◽  
Rate Increase ◽  
Short Circuit ◽  
Potential Drop ◽  
Short Circuit Current ◽  
Secretory Rate ◽  
Sudden Drop ◽  
Tissue Resistance ◽  
Per Se

Changing from 5% CO2 in the serosal solution only to 10% CO2 on both sides doubles the acid secretory rate of the bullfrog stomach (as shown previously) and raises the transmural potential difference, although the short-circuit current is not changed. The secretory overshoot on reoxygenation after anaerobiosis, observed in 5% CO2, is virtually eliminated in 10% CO2, as predicted by the diffusion model which explains the secretory rate increase. It was found that the rate of rise of the secretory rate during anoxia was identical in the 2 conditions, which explains the increased secretory lag in 10% CO2 and suggests an interesting limitation on the rate with which acid secretion can be activated. During anoxia in 10% CO2, but not in 5% CO2, there occurs a sudden drop in PD to a slightly negative value associated with a fall in tissue resistance. This effect occurs under SCN-inhibition and thus seems unrelated to H+ transport per se. A working model is presented which can explain some of the events surrounding the sudden potential drop.

Acid-base balance in amphibian gastric mucosa

1975 ◽  
Vol 229 (3) ◽  
pp. 721-730 ◽  
Author(s):  
W Silen ◽  
TE Machen ◽  
JG Forte
Keyword(s):  
Nutrient Solution ◽  
Marked Decrease ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Base Line ◽  
Acid Base Balance ◽  
Acid Base ◽  
Base Balance ◽  
Frog Stomach ◽  
Nutrient Solutions

It has been established that H+ secretion can be maintained in frog stomach in the absence of exogenous CO2 by using a nutrient bathing fluid containing 25 mM H2PO4 (pH approximately equal to 4.5) or by lowering the pH of a nonbuffered nutrient solution to about 3.0-3.6. Exogenous CO2 in the presence of these nutrient solutions uniformly caused a marked decrease in H+ secretion, PD, adn short-circuit current (Isc) and an increase in transmucosal resistance (R). Elevation of nutrient [k+] to 83 mM reduced R significantly but transiently without change in H+ when nutrient pH less than 5.0, whereas R returned to base line and H+ increased when nutrient pH greater than 5.0. Acidification of the nutrient medium in the presence of exogenous CO2 results in inhibition of the secretory pump, probably by decreasing intracellular pH, and also interferes with conductance at the nutrient membrane. Removal of exogenous CO2 from standard bicarbonate nutrient solution reduced by 50% the H+, PD, and Isc without change in R; K+-free nutrient solutions reverse these changes in Isc and PD but not in H+. The dropping PD and rising R induced by K+-free nutrient solutions in 5% CO2 - 95% O2 are returned toward normal by 100% O2. Our findings support an important role for exogenous CO2 in maintaining normal acid-base balance in frog mucosa by acting as an acidifying agent.

Effect of nicotine on gastric acid secretion: evidence of electrogenic pump theory.

1977 ◽  
Vol 232 (3) ◽  
pp. E251
Author(s):  
M A Dinno ◽  
M Ando ◽  
F H Dinno ◽  
K C Huang ◽  
W S Rehm
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Secretory Rate ◽  
Mucosal Membrane ◽  
Marked Inhibition ◽  
Linear Relationships ◽  
Hcl Secretion ◽  
Frog Stomach ◽  
Bathing Fluid

In vitro studies on H+ secretion, potential difference (PD), short-circuit current (Isc), and resistance across stripped mucosa of frog stomach in Cl-medium have shown that addition of nicotine in the serum bathing fluid caused a marked inhibition of the H+ secretory rate and an increase of PD and Isc without change of the transmucosal resistance. A dose-response correlation was indicated. During the first 8 min, the changes in the measured parameters, namely, PD versus Ih and Isc versus Ih, were linear. After 8 min, a deviation from linearity was observed. From the slope of the regression lines, the resistance of the electrogenic Cl- pump on the mucosal membrane (Rcl) was calculated to be 127 omega cm2 and the resistance of the chloride pathway on the serosal side (Rcl) was 407 omega cm2. The resistance of the H+ pump on the mucosal membrane (Rh) in Cl- medium was estimated to be 385 omega cm2. The sum of the emf's of the Cl+ pump on the mucosal membrane and of the Cl- gradient across the serosal membrane, namely Ecl + Ecl, was found to be 35 mV. The presence of such linear relationships between measured versus the H+ rate and Isc versus Ih lends support to the electrogenic theory of HCl secretion.

Acid secretion, potential difference, and resistance of elasmobranch stomach

1962 ◽  
Vol 203 (6) ◽  
pp. 1091-1093 ◽  
Author(s):  
Warren S. Rehm
Keyword(s):  
Gastric Mucosa ◽  
Acid Secretion ◽  
Present Report ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Potential Difference ◽  
Secretory Rate ◽  
Negaprion Brevirostris ◽  
Ion Secretion

The present report is concerned with in vitro studies on gastric mucosa of the skate, Raja eglentaria, the electric ray, Narcine braziliensis, and the shark, Negaprion brevirostris. Maximum secretory rates of from 0.65 to 2.7 µEq hr–1 cm–2 were found. An increase in the secretory rate from an initial low level was associated with an increase in potential difference (PD), a decrease in resistance, and an increase in the calculated short-circuit current. The average PD and resistance before the increase in the secretory rate was 2.2 mv (nutrient positive) and 268 ohms cm2. After the increase they were 6.4 mv and 199 ohms cm2. Thiocyanate (10–2 m) to nutrient resulted in a decrease of secretory rate to zero and an increase in PD and resistance. The results can be explained on the basis of the separate mechanisms theory of H+ and Cl– ion secretion on the assumption that the resistance in the Cl– ion limb of the circuit is considerably lower than that in the H+ ion limb of the circuit.

PARASYMPATHETIC ACTION ON GASTRIC BIOELECTRIC POTENTIAL IN RATS

1967 ◽  
Vol 45 (2) ◽  
pp. 281-290 ◽  
Author(s):  
H. Allan Ridley ◽  
Burton E. Vaughan ◽  
Joseph T. Cummins
Keyword(s):  
Acid Secretion ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Detectable Effect ◽  
Partial Recovery ◽  
Bioelectric Potential ◽  
Rat Stomach ◽  
Solution Bathing ◽  
Isolated Rat

The gastric bioelectric potential in vitro was consistently lower in stunned rats than in rats anesthetized with ether, or decapitated. This depressed potential was prevented by vagotomy and by atropine either subcutaneously injected or directly instilled. Similarly, transmural potential and short-circuit current were sharply reduced, by one-half, when the solution bathing the mucosal surface was made 10−2 M in acetylcholine (ACh). There was no detectable effect on transmural conductance (dI/dE). Inhibition of potential was proportional to ACh concentration from 10−5 M to 10−2 M. Partial recovery was demonstrated by rinsing and replacing solutions; atropine at 10−4 M irreversibly blocked such inhibition. Tubocurarine at 10−3 M did not change the response, when added prior to ACh, while physostigmine at 10−4 M enhanced the effect of ACh. The ACh analogues acetyl-β-methylcholine, acetylthiocholine, and carbamylcholine, at 10−3 M, reduced potential, as did ACh at 10−3 M. Carbamylcholine, which is not appreciably hydrolyzed by acetylcholinesterase, showed only slightly greater effect than ACh. In these studies, bioelectric potential was altered without any change in the acid secretion rate. This supports other studies demonstrating independence in the isolated rat stomach of electrical and acid secretion parameters.

Suppression of gastric acid secretion by furosemide in isolated gastric mucosa of guinea pig

1980 ◽  
Vol 239 (6) ◽  
pp. G532-G535 ◽  
Author(s):  
A. Ayalon ◽  
A. Corcia ◽  
G. Klemperer ◽  
S. R. Caplan
Keyword(s):  
Guinea Pig ◽  
Acid Secretion ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Electrical Conductance ◽  
Short Circuit Current ◽  
Cl Transport ◽  
Consequent Reduction ◽  
Net Flux ◽  
Mucosal Side

The effect of furosemide on acid secretion and Cl- transport was studied in isolated fundic mucosa of the guinea pig. Furosemide (10(-3) M), applied to the serosal side produced an immediate effect on the short-circuit current (Isc), lowering it by 47 +/- 2%. Potential difference decreased by 29 +/- 3%, electrical conductance by 18 +/- 4%, acid secretion by 38 +/- 1%, and net flux of Cl- from serosal-to-mucosal side by 37%. Application of the drug to the mucosal side produced similar effects on acid secretion and on the electrical parameters. It is suggested that furosemide blocks the entrance of Cl-, by the Na+--Cl- cotransport mechanism, through the basolateral membrane of the secreting cell. The consequent reduction in electrogenic Cl- transport would cause Isc and acid secretion to decrease. A reduction of Cl- conductance of the apical membrane, upon mucosal application of the drug, would cause similar effects on acid secretion and Cl- transport.

scholarly journals Acid-Base Transport and Control in Locust Hindgut: Artefacts Caused by Short-Circuit Current

1991 ◽  
Vol 155 (1) ◽  
pp. 455-467
Author(s):  
R. BRENT THOMSON ◽  
N. AUDSLEY ◽  
JOHN E. PHILLIPS
Keyword(s):  
Cyclic Amp ◽  
Acid Secretion ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Salt Bridges ◽  
Electrical Parameters ◽  
Acid Base ◽  
Before And After ◽  
And Control ◽  
Stimulation Of

The commonly used method of passing short-circuit current (Isc) across insect epithelia through Ag-AgCl electrodes, without the use of salt bridges, leads to significant OH− production at the cathode (lumen side) when high currents are applied. The alkalization of the lumen previously reported when cyclic AMP was added to short-circuited locust hindgut is a result of this phenomenon rather than cyclic-AMP-mediated stimulation of acid-base transport in the hindgut. When salt bridges are used to pass short-circuit current across locust hindgut, acid secretion (JH) into the lumen equals alkaline movement (JOH) to the haemocoel side, and JH is similar under both open- and short-circuit conditions. JH is similar (1.5 μequiv cm−2 h−1) in recta and ilea. Addition of cyclic AMP inhibits JH across the rectum by 42–66%, but has no effect on the ileum when salt bridges are used. Electrical parameters (Isc, Vt, Rt) reflecting hindgut Cl− transport (JCL) before and after stimulation with cyclic AMP are the same whether or not salt bridges are used. We found no evidence of any coupling between JCl and JH/JOH.

Further Observations on the Physiology of Salinity Adaptation in the Crab-Eating Frog (Rana Cancrivora)

1968 ◽  
Vol 49 (1) ◽  
pp. 185-193
Author(s):  
MALCOLM S. GORDON ◽  
VANCE A. TUCKER
Keyword(s):  
Sea Water ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Osmotic Concentration ◽  
Green Toad ◽  
The Face ◽  
Solution Bathing ◽  
Toad Bufo

1. Total rates of urea loss from adult euryhaline crab-eating frogs (Rana cancrivora) adapted to various environmental salinities between fresh water and 80 % sea water increase as salinity increases above 40% sea water. Oxygen consumption is constant in rate in all salinities studied. 2. The presence of urea in the Ringer solution bathing isolated pieces of skin of frogs adapted to 60% sea water increases both the electrical potential and the inwardly directed short-circuit current across the skin. 3. In skeletal muscle cells addition of intracellular solutes maintains tissue hydration in the face of large increases in plasma osmotic concentration in high-salinity media. Changes in the intracellular urea and free amino acid concentrations are primarily responsible for increases in intracellular osmotic concentration. 4. Some implications of these observations are discussed and comparisons made with the euryhaline green toad, Bufo viridis.

Sites of resistance changes with inhibition of acid secretion in frog stomach

1986 ◽  
Vol 250 (5) ◽  
pp. G639-G647
Author(s):  
W. S. Rehm ◽  
G. Carrasquer ◽  
M. Schwartz
Keyword(s):  
Acid Secretion ◽  
Proton Pump ◽  
Tubular Cell ◽  
Secretory Rate ◽  
Tubular Cells ◽  
Resistance Increase ◽  
Frog Stomach ◽  
Scn Resistance ◽  
Gastric Proton Pump ◽  
Resistance Decrease

The primary purpose of this study was to determine the sites of resistance changes from thiocyanate inhibition of secretion to better evaluate models of the gastric proton pump. The potential difference, resistance, and H+ secretory rate were measured with various tonicities of the secretory fluid. Thiocyanate (SCN) inhibition generally produces a resistance increase, but with nutrient Ba, the resistance is high and SCN decreases it. The latter effect is also seen with cimetidine. In the secreting fundus a hypotonic secretory solution has a small effect on resistance, but in the inhibited fundus the effect is huge, due to increase of resistance of the lumen-tubular cell pathway. With a hypotonic secretory solution, for inhibited fundus (cimetidine or omeprazole) and antrum, SCN does not decrease the resistance of the surface cells and/or the transintercellular pathways with or without Ba. The SCN resistance decrease with Ba is via the tubular cell pathway. With Ba the resistance of the nutrient membrane of the tubular cells decreases after SCN or cimetidine inhibition. The findings further support the concept that under standard conditions the resistance via the lumina and tubular cells is low and that via the surface cells and transintercellular pathways is high.

Effect of furosemide on the electrical parameters of frog skin

1982 ◽  
Vol 243 (6) ◽  
pp. F581-F587 ◽  
Author(s):  
A. Corcia ◽  
S. R. Caplan
Keyword(s):  
Active Transport ◽  
Frog Skin ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Relative Increase ◽  
Electrical Potential Difference ◽  
Electrical Parameters ◽  
Active Conductance ◽  
Solution Bathing

When added to the mucosal solution bathing isolated frog skin at concentrations ranging from 5 X 10(-4) to 3 X 10(-3) M, the diuretic furosemide increased both the active transport of sodium and the electrical potential difference across the tissue in a dose-dependent way. The same effect was observed in chloride-free solutions. Mucosal furosemide also decreased the passive unidirectional fluxes of chloride. We believe that as far as electrical parameters are concerned mucosal furosemide has a double effect in frog skin: it increases the active conductance to sodium across the mucosal membrane, thus increasing active transport, and decreases the passive permeability to chloride, thus altering the passive conductance of the skin. The relative increase in short-circuit current was, however, invariably greater than the increase of the active conductance, suggesting the influence of yet a third effect. The effect of mucosal furosemide on active sodium transport was blocked by amiloride (5 X 1-(-5) M) and was independent of vasopressin. Qualitatively the effect was similar to the effect produced by triphenylmethylphosphonium ion.

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