Effects of anions on sodium transport in toad urinary bladder

Singer, Irwin; Civan, MM

doi:10.1152/ajplegacy.1971.221.4.1019

Cited by 37 publications

(11 citation statements)

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“…2). in an extensive study Singer and Civan (1971) demonstrated that Na + transport across toad urinary bladder was influenced markedly by the anion which replaced mucosal C1-. The anion most effective in stimulating Na + transport was SCN-, while azide caused the most inhibition.…”

Section: I) Effects Of Mucosal Anionsmentioning

confidence: 99%

“…In most studies of Na + transport attention has focused on such transport with the tissue bathed in C1 Ringer's and few studies of the effects of medium anions have been published. Singer and Civan (1971), in a study in which a variety of anions replaced medium C1 , suggested that the effects of anion substitution on transepithelial Na + transport were mediated at one or more positively charged sites with relatively weak field strength. Finn (1980, 1983) applied microelectrode techniques to study effects of anion substitution in the mucosal and serosal media.…”

Section: Introductionmentioning

confidence: 99%

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Effects of anions on cellular volume and transepithelial Na+ transport across toad urinary bladder

et al. 1985

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The effects of complete substitution of gluconate for mucosal and/or serosal medium Cl- on transepithelial Na+ transport have been studied using toad urinary bladder. With mucosal gluconate, transepithelial potential difference (VT) decreased rapidly, transepithelial resistance (RT) increased, and calculated short-circuit current (Isc) decreased. Calculated ENa was unaffected, indicating that the inhibition of Na+ transport was a consequence of a decreased apical membrane Na+ conductance. This conclusion was supported by the finding that a higher amiloride concentration was required to inhibit the residual transport. With serosal gluconate VT decreased, RT increased and Isc fell to a new steady-state value following an initial and variable transient increase in transport. Epithelial cells were shrunken markedly as judged histologically. Calculated ENa fell substantially (from 130 to 68 mV on average). Ba2+ (3 mM) reduced calculated ENa in Cl- Ringer's but not in gluconate Ringer's. With replacement of serosal Cl- by acetate, transepithelial transport was stimulated, the decrease in cellular volume was prevented and ENa did not fall. Replacement of serosal isosmotic Cl- medium by a hypo-osmotic gluconate medium (one-half normal) also prevented cell shrinkage and did not result in inhibition of Na+ transport. Thus the inhibition of Na+ transport can be correlated with changes in cell volume rather than with the change in Cl-per se. Nystatin virtually abolished the resistance of the apical plasma membrane as judged by measurement of tissue capacitance. With K+ gluconate mucosa, Na+ gluconate serosa, calculated basolateral membrane resistance was much greater, estimated basolateral emf was much lower, and the Na+/K+ basolateral permeability ratio was much higher than with acetate media. It is concluded the decrease in cellular volume associated with substitution of serosal gluconate for Cl results in a loss of highly specific Ba2+-sensitive K+ conductance channels from the basolateral plasma membrane. It is possible that the number of Na+ pump sites in this membrane is also decreased.

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Section: I) Effects Of Mucosal Anionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of anions on cellular volume and transepithelial Na+ transport across toad urinary bladder

et al. 1985

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“…Substitution of gluconate or methylsulphate for CI, however, either slightly depressed Na transport or did not affect it. Several investigators have reported on the effects of anions on Na transport in tight epithelia (Singer & Civan, 1971;Turnheim, Frizzell & Schultz, 1977). However, the specific mechanism by which anions affect apical Na conductance is unknown.…”

Section: Electrophysiology Of Frog Skinmentioning

confidence: 99%

Cell K activity in frog skin in the presence and absence of cell current

et al. 1985

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Cell K activity, acK, was measured in the short-circuited frog skin by simultaneous cell punctures from the apical surface with open-tip and K-selective microelectrodes. Strict criteria for acceptance of impalements included constancy of the open-tip microelectrode resistance, agreement within 3% of the fractional apical voltage measured with open-tip and K-selective microelectrodes, and constancy of the differential voltage recorded between the open-tip and the K microelectrodes 30-60 sec after application of amiloride or substitution of apical Na. Skins were bathed on the serosal surface with NaCl Ringer and, to reduce paracellular Cl conductance and effects of amiloride on paracellular conductance, with NaNO3 Ringer on the apical surface. Under control conditions acK was nearly constant among skins (mean +/- SD = 92 +/- 8 mM, 14 skins) in spite of a wide range of cellular currents (5 to 70 microA/cm2). Cell current (and transcellular Na transport) was inhibited by either apical addition of amiloride or substitution of Na by other cations. Although in some experiments the expected small increase in acK after inhibition of cell current was observed, on the average the change was not significant (98 +/- 11 mM after amiloride, 101 +/- 12 mM after Na substitution), even 30 min after the inhibition of cell current. The membrane potential, which in the control state ranged from -42 to -77 mV, hyperpolarized after inhibition of cell current, initially to -109 +/- 5 mV, then depolarizing to a stable value (-88 +/- 5 mV) after 15-25 min. At this time K was above equilibrium (EK = 98 +/- 2 mV), indicating that the active pump mechanism is still operating after inhibition of transcellular Na transport. The measurement of acK permitted the calculation of the passive K current and pump current under control conditions, assuming a "constant current source" with almost all of the basolateral conductance attributable to K. We found a significant correlation between pump current and cell current with a slope of 0.31, indicating that about one-third of the cell current is carried by the pump, i.e., a pump stoichiometry of 3Na/2K.

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“…Hence, the inhibitory action on Na transport might arise from the binding of Fe 3 § to negatively charged groups associated with a carrier or a charged ion channel site in the outer cell membranes and/or from modifications in general surface charge. Studies by Biber and Mullen [6], Singer and Civan [28]~ and Zeiske and Lindemann [31] have indicated that charged sites may serve as filters or binding sites for the translocation of Na across the external surface of the frog skin.…”

Section: Discussionmentioning

confidence: 99%

“….... across the external surface of frog skin [1,6,28,31]. To further analyze the importance of charge interaction on active transport processes, we studied the effects of external Fe 3 § an ion which is very electropositive because of its high charge and small radius, on Na transport in the isolated skin of Rana pipiens.…”

Section: Average (~]-~)mentioning

confidence: 99%