TY - JOUR
T1 - Activation energy for water transport in toad bladder
AU - Eggena, P.
PY - 1983
Y1 - 1983
N2 - Activation energies (E(a)) 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 E(a) 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°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 E(a) measurements, bladders were exposed to ADH at room temperature, fixed with glutaraldehyde, and subjected to osmotic gradients at different temperatures. The E(a) values for osmotic water flow across these ADH-permeabilized, glutaraldehyde-fixed bladders were 5.1 (4-12°C), 4.3 (12-21°C), 3.6 (21-36°C), and 3.6 kcal/mol (30-38°C). E(a) values for shear viscosity of water in these temperature ranges were calculated to be 4.7, 4.2, 4.1 and 3.6 kcal/mol. respectively. The close correlation between E(a) values for bulk water viscosity and osmotic water flow across the bladder wall suggests that an equivalent number of hydrogen bonds must be broken to achieve and increase in water flow through ADH-induced channels and an increase in fluidity of water in bulk-solution.
AB - Activation energies (E(a)) 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 E(a) 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°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 E(a) measurements, bladders were exposed to ADH at room temperature, fixed with glutaraldehyde, and subjected to osmotic gradients at different temperatures. The E(a) values for osmotic water flow across these ADH-permeabilized, glutaraldehyde-fixed bladders were 5.1 (4-12°C), 4.3 (12-21°C), 3.6 (21-36°C), and 3.6 kcal/mol (30-38°C). E(a) values for shear viscosity of water in these temperature ranges were calculated to be 4.7, 4.2, 4.1 and 3.6 kcal/mol. respectively. The close correlation between E(a) values for bulk water viscosity and osmotic water flow across the bladder wall suggests that an equivalent number of hydrogen bonds must be broken to achieve and increase in water flow through ADH-induced channels and an increase in fluidity of water in bulk-solution.
UR - http://www.scopus.com/inward/record.url?scp=0020694026&partnerID=8YFLogxK
U2 - 10.1152/ajpcell.1983.244.1.c44
DO - 10.1152/ajpcell.1983.244.1.c44
M3 - Article
C2 - 6401402
AN - SCOPUS:0020694026
SN - 0363-6143
VL - 13
SP - C44-C49
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
IS - 1
ER -