Excretion of H+ and NH4+ by the urinary bladder of the acidotic toad and the effect of short-circuit current on the excretion

Frazier, Loy W.; Vanatta, John C.

doi:10.1016/0005-2736(71)90299-9

Cited by 52 publications

(18 citation statements)

References 10 publications

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“…These results confirm the studies by Frazier and Vanatta [9] and Ludens and Fanestil [16] that the urinary bladder of the toad, Bufo marinus, is able to acidify the solution bathing its mucosal surface, and document further by direct measurements of acid secretion that this ability depends upon the geographic origin of the toad. Bladders of toads of Colombian origin have acidifying capacity, whereas those from the Dominican Republic with rare exceptions have not.…”

Section: Discussionsupporting

confidence: 88%

Urinary acidification and carbonic anhydrase distribution in bladders of Dominican and Colombian toads

1974

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Summary.A comparative analysis of the acidifying capacity and distribution of carbonic anhydrase was made in isolated bladders of toads, Bufo marinus, obtained from the Dominican Republic (D) and Colombia (C). In the absence of exogenous CO2 and HCOS-, mucosal acidification was observed in 10 of the 18 C toad bladders examined and in only one of 18 D toad bladders. In approximately half of the C toad bladders the rate of acidification was measurable by means of the pH stat method; the average rate in this group was 0.22 + 0.03 lamoles/hour in the absence of exogenous COz and 0.35 _+ 0.04 lamoles/hour in the presence of 1% CO2. Rates were not measurable in D toad bladders with or without CO 2. Staining of whole stretched bladders for carbonic anhydrase revealed a population of enzyme-containing mucosal cells accounting for 4.6 % of the surface area in C toad bladders and 0.8 % in D toad bladders. Electron histochemistry of both bladders identified the carbonic anhydrase-containing cells as mitochondria-rich cells.Conflicting observations on the acidifying ability of the urinary bladder of the toad, Bufo marinus, have been attributed to the different geographical origin of the toads studied [16]. Whereas Leaf and coworkers [14,15]

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Section: Discussionsupporting

confidence: 88%

Urinary acidification and carbonic anhydrase distribution in bladders of Dominican and Colombian toads

1974

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“…A similar model has been proposed in rat kidney proximal tubule and small intestine (Pitts, Ayer & Schiess, 1949;Pitts, 1961;Murer, Hopfer & Kinne, 1976;Liedtke & Hopfer, 1977 as well as frog skin in vitro (Garcia-Romeu & Ehrenfeld, 1975;Alvarado, Dietz & Mullen, 1975), gills (Motais & Garcia-Romeu, 1972), gallbladder (Whitlock & Wheeler, 1969), and urinary bladder of the toad (Frazier & Vanatta, 1971) and turtle (Green, Steinmetz & Frazier, 1968; see also Sachs, et al, 1982). In choroid plexus Wright (1977) found that the buffer glycodiazine was about 50% more effective than HCO~ in stimulating the transepithelial Na § transport.…”

Section: Other Evidence For Na/h--hcojc1mentioning

confidence: 54%

Influx mechanisms for Na+ and Cl− across the brush border membrane of leaky epithelia: A model and microelectrode study

1983

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This paper presents a numerical model for the movement of Na+, K+, Cl-, H+ and HCO3- in a leaky epithelium. The model describes the active transport of Na+ and K+ at the serosal membrane and electrodiffusive permeation across the mucosal, serosal and junctional pathways. The model accounts for H+ and HCO3- production in the cell. The influx of Na+ and Cl- is assumed to occur mainly via Na/H and Cl/HCO3 exchange. The behavior of the cell, with this influx mechanism, is compared to a cell with an obligatory neutral coupled influx of Na+ and Cl-. All parameters are obtained from the literature, primarily from studies utilizing the Necturus gallbladder. The analysis shows (i) that it is virtually impossible in steady-state experiments to distinguish between cells with Na/H - HCO3/Cl transport and cells with Na/Cl transport mechanisms. (ii) That nonsteady-state experiments can decide whether Na/H - HCO3/Cl or Na/Cl transport mechanisms mediate the influx of salt. A comparison between studies with ion-selective microelectrodes and the model predictions indicates that the influx of Na+ and Cl- is mediated by Na/H - HCO3/Cl transport when the external solutions contain CO2 and HCO3. (iii) The model also explains the diuretic effects of furosemide and carbonic anhydrase inhibitor, as well as the stimulatory effects on salt transport of elevated levels of HCO3- at a constant pH. (iv) The model fails to explain some experiments performed in HCO3/Co2-free media and some experiments using inhibitors.

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“…It has been demonstrated under a variety of conditions that the short-circuit current is an excellent measure of net sodium transport in one subspecies of Bufo marinus, that obtained from the Dominican Republic [5]. Another subspecies, Colombian toads, have been shown to secrete hydrogen ions from serosal to mucosal side 'electrogenically' [3,9,13] and to absorb chloride ions [2]. No hydrogen ion secretion has been demonstrated in the Dominican toad [7,13].…”

Section: Discussionmentioning

confidence: 99%

Coupling of sodium transport to respiration in the toad bladder

1975

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Energy expenditure and transepithelial sodium transport were measured continuously and simultaneously from isolated urinary bladders of the Dominican toad, Bufo marinus. Sodium transport was measured as the short-circuit current and CO2 produced by the bladder was measured conductometrically by the method of Maffly. The rates of sodium transport and CO2 productions were linearly related. The slope of the regression of sodium transport on CO2 production, dJNa/dJCO2, was found to be quite similar in paired half bladders but to differ significantly between bladders from different toads. Thus, in this preparation there appears to be no unique stoichiometric ratio characterizing sodium transport and metabolism and past efforts to arrive at such a value by averaging results obtained from different animals do not seem warranted. The CO2 production by the isolated bladder which is unrelated to sodium transport was determined by two means: 1) extrapolating the regression of JNa on JCO2 to JNa equals O, and 2) measuring CO2 production with sodium transport suppressed by removal of all sodium from the mucosal bathing medium. The two methods gave values which were in close agreement in each preparationmthis suggests that metabolism which supports nontransport activities in this tissue cannot be recruited to support the energy requirement of sodium transport and vice versa.

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Excretion of H+ and NH4+ by the urinary bladder of the acidotic toad and the effect of short-circuit current on the excretion

Cited by 52 publications

References 10 publications

Urinary acidification and carbonic anhydrase distribution in bladders of Dominican and Colombian toads

Urinary acidification and carbonic anhydrase distribution in bladders of Dominican and Colombian toads

Influx mechanisms for Na+ and Cl− across the brush border membrane of leaky epithelia: A model and microelectrode study

Coupling of sodium transport to respiration in the toad bladder

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