Toad urinary bladder

J DeLong, MM Civan. (1983). Microelectrode study of K+ accumulation by tight epithelia. I. Baseline values of split frog skin and toad urinary bladder. J Membr Biol 72 183-193. 

The permeation of toad urinary bladder by 22 non-electrolytes is another example [50] ... 

According to the Onsager s relations, three coefficients are to be determined. They are the passive permeability to sodium ZNa, the metabolic reaction coefficient if there is no sodium transport Zr, and the cross-coefficient between the chemical reaction and the sodium flow ZNar. The linear nonequilibrium thermodynamics formulation for the active transport of sodium and the associated oxygen consumption in frog skin and toad urinary bladders are studied experimentally. Sodium flow JNa is taken as positive in the direction from the outer to the inner surface of the tissue. The term JT is the rate of suprabasal oxygen consumption assumed to be independent of the oxygen consumption associated with the metabolic functions. 

Gatzy JT, Reuss L, Finn AL. Amphotericin B and K-i- transport across excised toad urinary bladder. Am J Physiol 1979 237 F145-F156. 

Nephrogenic diabetes insipidus has been described in patients receiving foscarnet, either alone or associated with a distal renal tubular acidosis [66, 67, 68]. In fact, a recent review cited foscarnet as the second most common reported cause of drug-induced diabetes insipidus, second only to lithium [69]. In experiments using toad urinary bladders [70], serosal application of foscarnet enhanced water flow in the presence of submaximal ADH concentrations, but did not affect water transport in the absence of ADH or when maximal concentrations of ADH were used. Mucosal foscarnet did not affect water transport. Further studies are needed to clarify the mechanisms for altered water handling by the kidneys with foscarnet. 

In the toad urinary bladder, an experimental model of the mammalian collecting tubule, addition of hthium to the mucosal surface (but not to the serosal surface) markedly inhibited both basal and arginine vasopressin-stimulated water flow [50]. The concentration of mucosal lithium used in these studies (10 mEq/L) was comparable to or even lower than that usually found in the urine of patients on well-controlled lithium therapy (that is, 10 to 40 mEq/L) [63] Fernandez et al. [53] confirmed the inhibitory effect of lithium on water flow in toad urinary bladders exposed only submaximal concentrations of arginine vasopressin. Inhibition of cyclic adenosine monophosphate-stimulated water flow when lithium (2 mEq/L) was applied to the serosal surface of the toad bladder was reported in one study. Such an effect of lithium, when applied to the serosal surface has, to our knowledge, not been found by any other investigators. As herein discussed, the bulk of evidence supports the notion that the action of lithium on water transport is the result of its cell uptake from the luminal (apical) surface of the collecting tubule. 

Fernandez-Repollet E, LeFurgeyA, Hardy MA,TlsherCC. Structural and functional response of toad urinary bladder of LICI. Kidney Int 1983 24 719-730. 

In the toad urinary bladder, an experimental model of the mammalian collecting tubule, addition of lithium to the mucosal surface (but not to the serosal surface) markedly inhibited both basal and arginine vasopressin-stimulated water flow [45]. The concentration of mucosal lithium used in these studies (10 mEq/L) was comparable to or even lower than that usually found in the urine of patients on well-controlled lithium therapy (that is, 10 to 40 mEq/L) [55]. Fernandez et al. 

Figure 10.9.1 Equivalent circuits used to analyze the transient behavior of the toad urinary bladder membrane. Rq represents electrolyte resistance and Q is the dielectric capacitance of the membrane. The branches involving and R are used to account for the transfer of charge across the...

Figure 10.9.2 High-frequency plot of Z (t) v.y. Her for the toad urinary bladder membrane. [From A. A. Pilla and G. S. Margules, 7. Electrochem. Soc., 124, 1697 (1977), reprinted by permission of the publisher. The Electrochemical Society, Inc.]...

In recent studies, using antidiuretic hormone-treated toad urinary bladder, Levine and Worthington [52] have been able to demonstrate experimentally the presence of co-transport of labeled methylurea and, to a lesser degree, acetamide and urea with unlabeled methylurea. They concluded that the demonstrations of co-transport is consistent with the presence of ADH-sensitive amide-selective channels rather than a mobile carrier. 

In certain cases such as toad urinary bladder and mammalian kidney, the movement of small polar molecules, especially urea, are significantly increased by antidiuretic hormones [52], Recently, it has been found that urea and water transport across the toad bladder can be separately activated by low concentration of vasopressin or 8 Br-cAMP [57], Based on these studies it was concluded that membrane channels for water and small polar nonelectrolytes differ significantly in both their dimensions and densities. The solute channels are limited in number, have relatively large radii and carry only a small fraction of water flow. On the other hand, the water channels have small radii. These findings provide strong experimental support for the concept of membrane pores which we have been advocating (see Fig. 5 in [4]). In this respect it is not unreasonable to expect that PCMBS and phloretin would also inhibit the ADH-sensitive increase in the permeability of these systems to urea and other small polar nonelectrolytes. 

Burch, R.M. and Halushka, P.V. (1980). Thromboxane and stable prostaglandin endo-peroxide analogs stimulate water permeability in the toad urinary bladder. ]. Clin. Invest., 66, 1251-57... 

Zusman, T.R., Keiser, J.R. and Handler, J.S. (1977). Vasopressin-stimulated prostaglandin E biosynthesis in toad urinary bladder. J. Clin. Invest., 60, 1339-47... 

Halushka, P.V. and Burch, R.M. (1984). Effects of arachidonic acid metabolites on Ca fluxes and intracellular calcium in epithelial cells from the toad urinary bladder. In Braquet, P. et al. (eds.) Prostaglandin and Membrane Ion Transport, pp. 323-26. (New York Raven Press)... 

At the other extreme, some amphibian epithelia, such as frog abdominal skin and toad urinary bladder, behave as tight epithelia. These are characterised by a high transepithelial potential difference and resistance, and very low hydraulic conductivity, and the shunt conductance is only a small fraction of the total conductance. 

As a general rule, channels blocked by the pyrazine compounds are found only in tight but not leaky epithelia. Thus pyrazine carboxamides block sodium entry into the cells of the kidney distal tubule [149], salivary duct [150], colon [ISl] and epididymis [152], but not into the cells of the small intestine of kidney proximal tubule. Sodium channels sensitive to pyrazine carboxamides are not confined either to epithelia or to mammalian cells. For example, sodium entry into the cells of frog skin epithelium [153], toad urinary bladder [154], chicken coprodeum, fish gills of some species [ISS], body wall of the leech [155] and crustacean gills [155] are also sensitive. In addition, there are reports that sodium entry sites in ova [3] and erythrocytes [156] are also susceptible to the effects of the pyrazine derivatives. 

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