Summary
The effect of amiloride on the sensitivity to Na of the mucosal border of toad urinary bladder was investigated by recording Na concentration-dependent transepithelial potential difference (V t ) and the intracellular potential. When mucosal Na concentration was normal, amiloride added to the mucosal solution at 10−4 m markedly reduced the mucosal membrane potential (V m ) and altered the potential profile from a two-step type to a well type. Similar changes were observed when Na was totally eliminated from the mucosal medium. The serosal membrane potential was insensitive to amiloride and elimination of mucosal Na. In the absence of amiloride, theV t could be described by the Goldman-Hodgkin-Katz equation in the range of mucosal Na concentration from 0 to 16mm, and amiloride extended this concentration range. By using the Goldman-Hodgkin-Katz equation, Na permeability was calculated from the data ofV t 's obtained in the allowed ranges of Na concentration and compared before and after the addition of amiloride. The results show that Na permeability decreases to 1/600 of control when the maximum dose of amiloride (10−4 m) is applied. The relationship between Na permeability and amiloride concentration is well explained on the basis of assumptions that amiloride binds to the Na site of the mucosal border in one-to-one fashion and in a competitive manner with Na and that Na permeability reduces in proportion to increase in number of the sites bound with amiloride.
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Baer, J. E., Jones, C. B., Spitzer, S. A. Russo, H. F. 1967. The potassium-sparing and naturiuretic activity of N-amidino-3,5-diamino-6-chlorpyrazine-carboxamide hydrochloride (amiloride hydrochloride).J. Pharmacol. Exp. Ther. 157:472
Bentley, P. J. 1968. Amiloride: A potent inhibitor of sodium transport across the toad bladder.J. Physiol. (London) 195:317
Biber, T. U. L. 1971. Effect of changes in transepithelial transport on the uptake of sodium across the outer surface of the frog skin.J. Gen. Physiol. 58:131
Biber, T. U. L., Chez, R. A., Curran, P. F. 1966. Na transport across frog skin at low external Na concentrations.J. Gen. Physiol. 49:1161
Biber, T. U. L., Curran, P. F. 1970. Direct measurement of uptake of sodium at the outer surface of the frog skin.J. Gen. Physiol. 56:83
Cereijido, M., Curran, P. F. 1965. Intracellular electrical potentials in frog skin.J. Gen. Physiol. 48:543
Civan, M. M., Frazier, H. S. 1968. The site of the stimulatory action of vasopressin on sodium transport in toad bladder.J. Gen. Physiol. 51:589
Crabbé, J., de Weer, P. 1969. Relevance of sodium transport pool measurements in toad bladder tissue for the elucidation of the mechanism whereby hormones stimulate active sodium transport.Pfluegers Arch. 313:197
Cuthbert, A. W., Shum, W. K. 1974. Amiloride and the sodium channel.Naunyn-Schmideberg's Arch. Pharmacol. 281:261
Ehrlich, E. N., Crabbé, J. 1968. The mechanism of action of amipramizide.Pfluegers Arch. 302:79
Eisenman, G. 1965. The electrochemistry of cation-sensitive glass electrodes.In. Advance in Analytical Chemistry and Instrumentation. C. N. Reilley, editor. Vol. 4, p. 213. Academic Press, New York
Erlij, D., Smith, M. W. 1973. Sodium uptake by frog skin and its modification by inhibitors of transepithelial sodium transport.J. Physiol. (London) 228:221
Frazier, H. S. 1962. The electrical potential profile of the isolated toad bladder.J. Gen. Physiol. 23:515
Frazier, L. W. 1974. Interrelationship of H+ excretion and Na+ reabsorption in the toad urinary bladder.J. Membrane Biol. 19:267
Frazier, L. W., Vanatta, J. C. 1973. Characteristics of H+ and NH +4 excretion by the urinary bladder of the toad.Biochim. Biophys. Acta 241:20
Glitzer, H.S. 1966. N-amidino-3,5-diamino-6-chloropyrazine-carboxamide; an active diuretic in the carboxamide series.Nature (London) 212:191
Herrera, F. C. 1972. Inhibition of lithium transport across toad bladder by amiloride.Am. J. Physiol. 222:499
Hill, B. 1971. The permeability of the sodium channel to organic cations in myelinated nerve.J. Gen. Physiol. 58:599
Koefoed-Johnsen, V., Ussing, H. H. 1958. The nature of the frog skin potentialActa Physiol. Scand. 42:298
Larramendi, L. M. H., Lorente, De Nó. R., Vidal, F. 1956. Restoration of sodium-deficient frog nerve fibers by an isotonic solution of guanidinium chloride.Nature (London) 178:316
Leb, D. E., Hoshiko, T., Lindley, B. D. 1965. Effects of alkali metal cations on the potential across toad and bullfrog urinary bladder.J. Gen. Physiol. 48:527
Lindley, B. D., Hoshiko, T. 1964. The effects of alkali metal cations and common anions on the frog skin potential.J. Gen. Physiol. 47:749
Macknight, A. D. C., Mortimer, M. C., Leaf, A. 1975. The sodium transport pool in toad urinary bladder epithelial cells.J. Membrane Biol. 20:365
Marumo, F., Asano, Y., Sasaoka, T., Koshikawa, S. 1967. Effect of tetrodotoxin on the sodium transport of the toad bladder.Proc. Japan. Acad. 43:407
Moreno, J. H., Reisin, I. L., Rodriguez, B. E., Rotunno, C. A., Cereijido, M. 1973. Barriers to sodium movement across frog skin.J. Membrane Biol. 11:99
Nagel, W., Dörge, A. 1970. Effect of amiloride on sodium transport of frog skin.Pfluegers Arch. 317:84
Reuss, L., Finn, A. L. 1974. Passive electrical properties of toad urinary bladder epithelium.J. Gen. Physiol. 64:1
Reuss, L., Finn, A. L. 1975a. Effects of changes in the composition of the mucosal solution on the electrical properties of the toad urinary bladder epithelium.J. Membrane Biol. 20:191
Reuss, L., Finn, A. L. 1975b. Dependence of serosal membrane potential on mucosal membrane potential in toad urinary bladder.Biophys. J. 15:71
Rick, R., Dörge, A., Nagel, W. 1975. Influx and efflux of sodium at the outer surface of frog skin.J. Membrane Biol. 22:183
Rotunno, C. A., Vilallonga, F. A., Fernández, M., Cereijido, M. 1970. The penetration of sodium into the epithelium of the frog skin.J. Gen. Physiol. 55:716
Salako, L. A., Smith, A. J. 1970. Changes in sodium pool and kinetics of sodium transport in frog skin produced by amiloride.Br. J. Pharmacol. 39:99
Singer, C. I., Civan, M. M. 1971. Effects of anions on sodium transport in toad urinary bladder.Am. J. Physiol. 221:1019
Urakabe, S., Handler, J. S., Orloff, J. 1970. Effect of hypertonicity on permeability properties of the toad bladder.Am. J. Physiol. 218:1179
Watanabe, A., Tasaki, I., Singer, I., Lerman, L. 1967. Effects of tetrodotoxin on excitability of squid giant axons in sodium-free media.Science 155:95
Zeiske, W., Lindemann, B. 1974. Chemical stimulation of Na+ current through the outer surface of frog skin epithelium.Biochim. Biophys. Acta 352:323
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Sudou, K., Hoshi, T. Mode of action of amiloride in toad urinary bladder. J. Membrain Biol. 32, 115–132 (1977). https://doi.org/10.1007/BF01905212
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DOI: https://doi.org/10.1007/BF01905212