Summary
The Na conductance of the apical membrane of the toad urinary bladder was measured at different concentrations of Na both in the external medium and in the cell. Bladders were bathed in high K-sucrose medium to reduce basal-lateral resistance and voltage, and the transepithelial currents measured under voltage-clamp conditions. Amiloride was used as a specific blocker of the apical Na channel. At constant external Na, the internal Na concentration was increased by blocking the basallateral Na pump with ouabain. With high Na activity in the mucosal medium (86mm), increases in intracellular Na activity from 10 to over 40mm increased the amiloride-sensitive slope conductance at zero voltage while apical Na permeability, estimated from current-voltage plots using the constant field equation, decreased by less than 20%. Lowering the serosal Ca concentration from 1 to 0.1mm had no effect on the change inP Na with increasing Nac, but increasing serosal Ca to 5mm enhanced the reduction inP Na with increasing Na c , presumably by increasing Ca influx into the cell.P Na was also reduced by serosal vanadate (0.5mm), a putative blocker of ATP-dependent Ca extrusion from the cell, and by acute exposure to CO2, which presumably acidifies the cytoplasm. Current-voltage relationships of the amiloridesensitive transport pathway were also measured in the absence of a Na gradient across the apical membrane. These plots show that outward current passes through the channels somewhat less easily than does inward current. The shape of theI-V relationships was not significantly altered by changes in cellular Na, Ca or H, indicating that the effects of these ions onP Na are voltage independent.
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Balfour, W.E., Grantham, J.J., Glynn, I.M. 1978. Vanadate stimulated natriuresis.Nature (London) 275:768
Beauwens, R., Crabbé, J., Rentmeesters, M. 1981. Effects of vanadate on the functional properties of the isolated toad bladder.J. Physiol. (London) 310:293–305
Begenisich, R., Danko, M. 1983. Hydrogen ion block of the sodium pore in squid giant axon.J. Gen. Physiol. 82:599–618
Benzanilla, F., Armstrong, C.M. 1972. Negative conductance caused by entry of sodium and cesium ions into the potassium channel of squid axons.J. Gen. Physiol. 60:588–602
Boron, W.F., Boulpaep, E. 1983. Intracellular pH regulation in the renal proximal tubule of the salamander.J. Gen. Physiol. 81:29–52
Boron, W.F., DeWeer, P. 1976. Intracellular pH transients in squid giant axons caused by CO2, NH3 and metabolic inhibitors.J. Gen. Physiol. 67:91–112
Cantley, L.C., Jr., Josephson, L., Warner, R., Yanagisawa, M., Lechene, C., Guidotti, G. 1978. Vanadate is a potent (Na,K)-ATPase inhibitor found in ATP derived from muscle.J. Biol. Chem. 252:F421-F423
Chase, H.S., Jr., Al-Awqati, Q. 1981. Regulation of the sodium permeability of the luminal border of the toad bladder by intracellular sodium and calcium.J. Gen. Physiol. 77:693–712
Chase, H.S., Jr., Al-Awqati, Q. 1983. Calcium reduces the sodium permeability of luminal membrane vesicles from toad bladder.J. Gen. Physiol. 81:643–665
Coronado, R., Miller, C. 1982. Conduction and block by organic cations in a K+-selective channel from sarcoplasmic reticulum incorporated into planar phospholipid bilayers.J. Gen. Physiol. 79:529–547
DiPolo, R. 1978. Ca pump driven by ATP in squid axons.Nature (London) 274:390–392
DiPolo, R., Beaugé, L. 1981. The effects of vanadate on calcium transport in dialyzed squid axons. Sidedness of vanadatecation interactions.Biochim. Biophys. Acta 645:229–237
DiPolo, R., Beaugé, L. 1982. The effect of pH on Ca+2 extrusion mechanisms on dialyzed squid axons.Biochim. Biophys. Acta 688:237–245
DiPolo, R., Rojas, H., Beaugé, L.A. 1979. Vanadate inhibits uncoupled Ca efflux but not Na−Ca exchange in squid axons.Nature (London) 281:228–229
Eaton, D.C., 1981. Intracellular sodium low activity and sodium transport in rabbit urinary bladder.J. Physiol. (London) 316:527–544
Eaton, D.C., Brodwick, M.S. 1980. Effects of barium on the potassium conductance of squid.J. Gen. Physiol. 75:727–750
Eaton, D.C., Hamilton, K., Johnson, K.E. 1984. Intracellular acidosis blocks the basolateral Na−K pump in rabbit urinary bladder.Biophys. J. 45:301a
Edmonds, D.T. 1982. Modelling the control mechanism of the Na channel in apical membrane of tight epithelia.Proc. R. Soc. London B 217:111–115
Eyring, H., Lumry, R., Woodbury, J.W. 1949. Some applications of modern rate theory to physiological systems.Rec. Chem. Prog. 10:100–114
Fuchs, W., Hviid Larsen, E., Lindemann, B. 1977. Current voltage curve of sodium channels and concentration dependence of sodium permeability in frog skin.J. Physiol. (London) 267:137–166
Garty, H., Lindemann, B. 1984. Feedback inhibition of sodium uptake in K+-depolarized toad urinary bladders.Biochim. Biophys. Acta 771:89–98
Gmaj, P., Murer, H., Kinne, R. 1979. Calcium ion transport across plasma membranes isolated from rat kidney cortex.Biochem. J. 178:549–557
Grinstein, S., Erlij, D. 1978. Intracellular Ca++ and the regulation Na+ transport in the frog skin.Proc. R. Soc. London B 202:353–360
Helman, S.I. 1981. Electrical rectification of the sodium flux across the apical barrier of frog skin epithelium.In: Ion Transport by Epithelia. S.G. Schultz, editor. pp. 15–30. Raven, New York
Hille, B. 1975. Ion selectivity, saturation and block in sodium channels. A four barrier model.J. Gen. Physiol. 66:535–560
Läuger, P. 1973. Ion transport through pores: A rate theory analysis.Biochim. Biophys. Acta 311:423–441
Lewis, S.A., Diamond, J.M. 1976. Na+ transport by rabbit urinary bladder, a tight epithelium.J. Membrane Biol. 28:1–40
Li, J.H.-Y., Palmer, L.G., Edelman, I.S., Lindemann, B. 1982. The role of sodium-channel density in the natriferic response of the toad urinary bladder to an antidiuretic hormone.J. Membrane Biol. 64:77–89
Lindemann, B. 1982. Dependence of ion flow through channels on the density of fixed charges at the channel opening. Voltage control of inverse titration curves.Biophys. J. 39:15–22
Lopez, V., Stevens, T., Lindquist, R.N. 1976. Vanadium ion inhibition of alkaline phosphatase-catalyzed phosphate ester hydrolysis.Arch. Biochem. Biophys. 175:31–38
Meech, R.W., Thomas, R.C. 1977. The effect of calcium injection on the intracellular sodium and pH of snail neurones.J. Physiol. (London) 265:867–879
Morel, F., LeBlanc, G. 1975. Transient current changes and Na compartmentalization in frog skin epithelium.Pfluegers Arch. 358:135–157
Palmer, L.G. 1982a. Na+ transport and flux ratio through apical Na+ channels in toad bladder.Nature (London) 297:688–690
Palmer, L.G. 1982b. Ion selectivity of the apical membrane Na channel in the toad urinary bladder.J. Membrane Biol. 67:91–98
Palmer, L.G. 1984a. Use of potassium depolarization to study apical transport properties in epithelia.Curr. Top. Membr. Trans. 20:105–121
Palmer, L.G. 1984b. Voltage dependent block by amiloride and other monovalent cations of apical Na channels in the toad urinary bladder.J. Membrane Biol. 80:153–165
Palmer, L.G., Edelman, I.S., Lindemann, B. 1980. Current-voltage analysis of apical sodium transport in toad urinary bladage analysis of apical sodium transport in toad urinary bladder: Effects of inhibitors of transport and metabolism.J. Membrane Biol. 57:59–71
Rossi, J.P.F.C., Garrahan, P.J., Rega, A.F. 1981. Vanadate inhibition of active Ca+2 transport across human red cell membranes.Biochim. Biophys. Acta 648:145–150
Schatzmann, H.J. 1966. ATP-dependent Ca++ extrusion from human red cells.Experientia 22:364–368
Taylor, A., Windhager, E.E. 1979. Possible role of cytosolic calcium and Na−Ca exchange in regulation of transepithelial sodium transport.Am. J. Physiol. 236:F505-F512
Thomas, S.R., Suzuki, Y., Thompson, S.M., Schultz, S.G. 1983. The electrophysiology ofNecturus urinary bladder. I. “Instantaneous” current-voltage relations in the presence of varying mucosal sodium concentrations.J. Membrane Biol. 73:157–175
Thompson, S.M., Suzuki, Y., Schultz, S.G. 1982. The electrophysiology of rabbit descending colon. I. Instantaneous transepithelial current-voltage relations and the current-voltage relations of the Na-entry mechanism.J. Membrane Biol. 66:41–54
Turnheim, K., Frizzell, R.A., Schultz, S.G. 1978. Interaction between cell sodium and the amiloride-sensitive sodium entry step in rabbit colon.J. Membrane Biol. 39:233–256
Ussing, H.H., Zerahn, K. 1951. Active transport of sodium as the source of electric current in the short-circuited frog skin.Acta Physiol. Scand. 23:110–127
Van Driessche, W., Erlij, D. 1983. Noise analysis of inward and outward Na+ currents across the apical border of ouabaintreated frog skin.Pfluegers Arch. 398:179–188
Van Driessche, W., Lindemann, B. 1979. Concentration dependence of currents through single sodium-selective pores in frog skin.Nature (London) 282:519–520
Van Etten, E.L., Waymack, P.P., Rehkop, D.M. 1974. Transition metal ion inhibition of enzyme-catalyzed phosphate ester displacement reactions.J. Am. Chem. Soc. 96:6782–6785
Woodbury, J.W., White, S.H., Mackey, M.C., Hardy, W.L., Chang, D.B. 1970. Bioelectrochemistry.In: Electrochemistry. H. Eyring, W. Jost and D. Henderson, editors. Chapter 9. Academic, New York
Woodhull, A.M. 1973. Ionic blockage of sodium channels.J. Gen. Physiol. 61:687–708
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Palmer, L.G. Modulation of apical Na permeability of the toad urinary bladder by intracellular Na, Ca, and H. J. Membrain Biol. 83, 57–69 (1985). https://doi.org/10.1007/BF01868738
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DOI: https://doi.org/10.1007/BF01868738