Laboratory Investigation

Kidney International (1979) 15, 513–519; doi:10.1038/ki.1979.66

pH-Dependence of water and solute transport in toad urinary bladder

Christos P Carvounis1, Sherman D Levine1 and Richard M Hays1

1Division of Nephrology, Albert Einstein College of Medicine, Bronx, New York

Correspondence: Dr R M Hays, Division of Nephrology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA

Received 3 April 1978; Revised 26 October 1978.

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Abstract

pH-Dependence of water and solute transport in toad urinary bladder. Stimulation of urea and water transport by vasopressin (ADH) appears to occur via independent pathways. We examined the effects of altering serosal or mucosal bath pH on transport of water, urea, and sodium. Compared to bladders with a serosal bath pH of 7.4 to 8.0, reducing the serosal bath pH to 6.8 led to a 60% fall in ADH-stimulated osmotic water flow, without decreasing the permeability of urea. Raising the serosal pH to 9.5 had the opposite effect: urea permeability was inhibited by 40% without altering water flow. Exogenous cyclic AMP-stimulated water and urea permeabilities were not dissociated, but were changed in the same direction by alterations in serosal pH: serosal acidification enhanced the effect of exogenous cyclic AMP on both urea and water, whereas the cyclic AMP effect on both was diminished by serosal alkalinization. This was especially marked for urea, suggesting that an alteration in the urea response to cyclic AMP may be particularly important in defining vasopressin-stimulated urea permeability as the serosal bath pH is altered. Mucosal acidification increased short circuit current but decreased both the urea and water response to ADH and 8-bromo-cyclic AMP. The response to cyclic AMP was less consistent. Mucosal alkalinization did not cause significant changes in either basal or stimulated transport. The data demonstrate distinct and separable effects of bath pH alterations on each of the transport systems examined.

Dépendance vis-à-vis du pH du transport d'eau et de substances dissoutes dans la vessie du crapaud. La stimulation du transport d'urée et d'eau par la vasopressine (ADH) parait être effectuée par des voies indépendantes. Dans ce travail nous avons étudié l'effet des modifications du pH du bain séreux ou muqueux sur le transport de l'eau, de l'urée et du sodium. Par comparaison avec des vessies dont le bain séreux est à pH 7,4 à 8,0 l'abaissement du pH du côté séreux à 6,8 détermine une diminution de 60% du débit osmotique d'eau sous stimulation par l'ADH, sans abaissement de la perméabilité à l'urée. L'augmentation du pH séreux à 9,5 a l'effet opposé: la perméabilité à l'urée est inhibée de 40% sans modification du débit d'eau. Les perméabilités à l'eau et à l'urée sous stimulation par cAMP ne sont pas dissociées mais sont modifiées dans le même sens par les changements du pH séreux: l'acidification augmente l'effet de cAMP exogène à la fois sur l'eau et l'urée alors que ces deux effets sont diminués par l'alcalinisation séreuse. Cela est particulièrement net pour l'urée, ce qui suggère qu'une modification du comportement de l'urée sous l'influence de cAMP peut être particulièrement importante pour définir la perméabilité à l'urée stimulée par la vasopressine quand le pH séreux est changé. L'acidification du côté muqueux augmente le courant de court-circuit mais diminue les réponses de l'urée et de l'eau à l'ADH et au 8-Br-cAMP. La réponse à l'AMP cyclique est moins nette. L'alcalinisation du côté muqueux ne détermine de modification ni du transport basal, ni du transport stimulé. Ces résultats démontrent des effets distincts et séparables des modifications du pH sur chacun des systèmes de transport étudiés.

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