Urea transport across urinary bladder and salt acclimation in toad (Bufo viridis)

The fluxes of urea across the urinary bladder of the toad Bufo viridis have been studied under conditions of acclimation to tap water or 500 mosM NaCl solution. The [14C]urea fluxes were measured simultaneously with [3H]inulin to test for nonspecific leakage. The fluxes are quite high (Ktrans = 75 x...

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Bibliographic Details
Published inThe American journal of physiology Vol. 258; no. 4 Pt 2; p. R883
Main Authors Shpun, S, Katz, U
Format Journal Article
LanguageEnglish
Published United States 01.04.1990
Subjects
Adaptation, Physiological
Animals
Biological Transport
Bufonidae - metabolism
Colforsin - pharmacology
Dinitrophenols - pharmacology
In Vitro Techniques
Mucous Membrane - metabolism
Phloretin - pharmacology
Serous Membrane - metabolism
Sodium - pharmacology
Sodium Chloride - pharmacology
Theophylline - pharmacology
Urea - analogs & derivatives
Urea - metabolism
Urinary Bladder - metabolism
Vasopressins - pharmacology
Water - metabolism
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Summary:The fluxes of urea across the urinary bladder of the toad Bufo viridis have been studied under conditions of acclimation to tap water or 500 mosM NaCl solution. The [14C]urea fluxes were measured simultaneously with [3H]inulin to test for nonspecific leakage. The fluxes are quite high (Ktrans = 75 x 10(-7) cm/s at 5 mmol/l urea) and are similar in either the mucosal-to-serosal or the opposite direction. "Summer" rates were five to six times higher than the "winter" rates. Antidiuretic hormone (ADH), theophylline, and forskolin increased the fluxes to variable degrees (two to five times), similar in the two acclimation conditions. Phloretin inhibited the urea fluxes by nearly 50%. 1,3-Dimethylurea and thiourea, but not acetamide, competed with the urea fluxes effectively. The fluxes of urea were not affected by the osmotic water flow, although both responded to ADH. It is concluded that urea transport across the urinary bladder of B. viridis is by facilitated diffusion through a specific pathway independent of water flux. The inhibitory effect of the structural analogues on the urea flux was affected by salt acclimation, whereas most other characteristics did not differ significantly at 5 mmol/l external urea under the two conditions of acclimation.
ISSN:0002-9513
DOI:10.1152/ajpregu.1990.258.4.r883