PMID: 6401402Jan 1, 1983Paper

Activation energy for water transport in toad bladder

The American Journal of Physiology
P Eggena

Abstract

Activation energies (Ea) for water movement across vasopressin-(ADH) sensitive epithelia have been reported to be about 10 kcal/mol (1, 12). The present study shows that measurements of Ea for osmotic water flow across toad bladders are unreliable, because a temperature change induces marked alterations in membrane permeability to water within a 2.5-min interval. Thus bladders equilibrated with ADH either at room temperature or at 33 degrees C and then suddenly subjected to a lower temperature were found to exhibit a marked increase in membrane permeability to water. This observation suggests that there is a rapid turn-over of water permeability sites and that sudden exposure to cold inhibits the removal more than the induction of sites by ADH. To stabilize ADH-induced water channels for Ea measurements, bladders were exposed to ADH at room temperature, fixed with glutaraldehyde, and subjected to osmotic gradients at different temperatures. The Ea values for osmotic water flow across these ADH-permeabilized, glutaraldehyde-fixed bladders were 5.1 (4-12 degrees C), 4.3 (12-21 degrees C), 3.6 (21-36 degrees C), and 3.6 kcal/mol (30-38 degrees C). Ea values for shear viscosity of water in these temperature ranges were calculated t...Continue Reading

References

Sep 1, 1978·The Journal of General Physiology·P A Rosenberg, A Finkelstein
May 1, 1972·The Journal of General Physiology·P Eggena
Jun 1, 1973·The Journal of Clinical Investigation·S LevineR M Hays
Apr 17, 1980·Nature·S Gluck, Q Al-Awqati
May 1, 1981·Proceedings of the Society for Experimental Biology and Medicine·P Eggena, A Gibas

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Citations

Dec 8, 2009·Biochemistry. Biokhimii︠a︡·Shu-Jing HaoGuo-Jiang Zhang
Oct 1, 1990·General and Comparative Endocrinology·P Mayers, P Couillard

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