Reversal by potassium of an effect of barium on the frog gastric mucosa

Ad, Pacifico; Schwartz, Manuel; Tn, Mackrell; Spangler, S.G.; Sanders, SS; Rehm, Warren S.

doi:10.1152/ajplegacy.1969.216.3.536

Cited by 41 publications

(8 citation statements)

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“…The addition of 0.1 mM BaCl2 to the nutrient side of the frog gastric mucosa has been shown (Jacobson, Schwartz, and Rehm, 1965;Schwartz, MacKrell, Jacobson, and Rehm, 1966;Schwartz, Pacifico, MacKrell, Jacobsen, and Rehm, 1968) to result in a large increase in the transmural resistance, without, however, markedly changing the acid secretory rate or potential difference. It appears that the primary action of Ba++ is to reversibly decrease the permeability of the nutrient membrane to K+ (Pacifico and Rehm, 1967;Rehm, 1967;Sachs and Pacifico, 1968;Pacifico, Schwartz, MacKrell, Spangler, Sanders, and Rehm, 1969). The magnitude of the long time-constant transient is also greatly reduced (Rehm, 1967), an observation consistent with our model.…”

Section: Prediction Of the Ba++ Effectsupporting

confidence: 83%

A Model for the Long Time-Constant Transient Voltage Response to Current in Epithelial Tissues

Kidder¹,

Rehm²

1970

Biophysical Journal

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Upon passing a step current through the frog gastric mucosa, a transient response in voltage is observed, which can formally be represented by several types of model systems, although some models require elements which are hard to visualize in terms of the known morphology of the mucosa. A physically reasonable model can be constructed by considering the changes in intracellular ionic composition which arise due to current flow, and the consequent changes in diffusion potentials across the two cell membranes. A simple model has been developed which fits the observed long time-constant portion of the transient at low current densities, and predicts departures from exponential behavior at larger currents. Since reasonable values for membrane resistance and cell volume give a fit, it is proposed that this model may account for the long time-constant portion of the transient response. There is no reason to expect that similar considerations do not hold for epithelial tissues in general.

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Section: Prediction Of the Ba++ Effectsupporting

confidence: 83%

A Model for the Long Time-Constant Transient Voltage Response to Current in Epithelial Tissues

Kidder¹,

Rehm²

1970

Biophysical Journal

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“…3). Barium seems to act primarily by reducing the passive K § conductance (Nagel, 1979;Nielsen, 1979), consistent with its effect on other tissues (Pacifico et al, 1969;Hermsmeyer & Sperelakis, 1970); the Na § pump remains active in the presence of Ba 2 § (Nagel, 1979;Nielsen, 1979). This approach may be of assistance to other investigators in confirming the intracellular placement of micropipettes and microelectrodes.…”

Section: Discussionsupporting

confidence: 63%

Microelectrode study of K+ accumulation by tight epithelia: I. Baseline values of split frog skin and toad urinary bladder

DeLong

Civan

1983

J. Membrain Biol.

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Toad bladder and split frog skin were impaled with fine-tipped single- and double-barrelled K+-selective microelectrodes. In order to circumvent membrane damage induced by impaling toad bladder, a null point method was developed, involving elevations of mucosal potassium concentration. The results suggest that intracellular potassium activity of short-circuited toad bladder is approximately 82 mM, twice as large as earlier estimates. Far more stable and rigorously defined intracellular measurements were recorded from short-circuited split frog skins. The intracellular positions of the micropipette and microelectrode tips were verified by transient hyperpolarizations of the membrane potential with mucosal amiloride or by transient depolarizations with serosal barium or strophanthidin. Simultaneous impalement of distant cells with separate micropipettes demonstrated that both the baseline membrane potentials and the responses to depolarizing agents were similar, further documenting that frog skin is a functional syncytium. Measurements with double-barrelled microelectrodes and simultaneous single-barrelled microelectrodes and reference micropipettes suggest that the intracellular potassium activity is about 104 mM, lower than previously reported. Taken together with measurements of intracellular potassium concentration, this datum suggests that potassium is uniformly distributed within the epithelial cells.

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“…Ba2+ is known to block K+ channels in a number of tissues (see Hermsmeyer & Sperelakis, 1970) and this effect explains many of its actions. In frog skin (Nagel, 1979), kidney tubule (Planelles, Teulon & Anagnostopoulos, 1981) and stomach (Pacifico, Schwartz, MacKrell, Spangler, Sanders & Rehm, 1969) the response to Ba2+ is reversed by an increased K+ concentration and a reduction in K+ conductance is, therefore, suggested as the basis of Ba2+ action. In the colon, increasing the serosal K+ concentration to 20 mm caused a significant inhibition of the BaCl2 response (Fig.…”

Section: Discussionmentioning

confidence: 99%

The secretory action of barium chloride in rat colon.

Hardcastle¹,

Hardcastle²,

Noble³

1985

The Journal of Physiology

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SUMMARY1. BaCl2, applied serosally, caused a rise in the p.d. and short-circuit current (s.c.c), and a decrease in tissue resistance in stripped sheets of rat colon. This response was dose dependent. Mucosal application of BaCl2 was without effect.2. The BaCl2-induced rise in s.c.c. was inhibited by reducing the serosal Na+ concentration to 25 mm. Lowering the mucosal Na+ concentration was without effect.3. Ouabain (10-3 M in serosal fluid) and furosemide (10-3 M in serosal fluid) both reduced the rise in s.c.c. induced by BaCl2.4. Flux determinations indicated that BaCl2 inhibited Na+ absorption and stimulated Cl-secretion by the colon.5. In vivo, BaCl2 increased fluid accumulation within the colonic lumen, an effect that was associated with a rise in the transcolonic p.d.6. Increasing the serosal K+ concentration to 20 mm reduced the responses to BaCl2, acetylcholine and theophylline, and this could not be entirely accounted for by the concomitant reduction in the serosal Na+ concentration. As high serosal K+ did not mimic the secretary response it would appear that BaCl2 does not act by blocking K+ channels.7. The rise in s.c.c. induced by BaCl2 was not reduced by Ca2+-free conditions, but it was inhibited by 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8) and trifluoperazine.8. BaCl2 did not alter cyclic AMP production by colonic scrapes. 9. It is concluded that BaCl2 induces colonic secretion by the release of intracellular Ca2+, which then combines with calmodulin to activate the secretary process.

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Reversal by potassium of an effect of barium on the frog gastric mucosa

Cited by 41 publications

References 0 publications

A Model for the Long Time-Constant Transient Voltage Response to Current in Epithelial Tissues

A Model for the Long Time-Constant Transient Voltage Response to Current in Epithelial Tissues

Microelectrode study of K+ accumulation by tight epithelia: I. Baseline values of split frog skin and toad urinary bladder

The secretory action of barium chloride in rat colon.

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