AJP - Renal Physiology, Vol 248, Issue 2 260-F265, Copyright © 1985 by American Physiological Society
Regulation of water permeability in toad urinary bladder at two barriers
W. A. Kachadorian, S. Sariban-Sohraby and K. R. Spring
The effects of prostaglandin synthesis inhibition by naproxen were studied
in toad bladder. Luminal membrane water permeability was evaluated both by
the frequency of intramembranous particle aggregates in granular cell
luminal membrane and by direct assessment of the rate of change of cell
volume during perfusion of an anisosmotic solution. Total tissue water
permeability was assessed by transbladder osmotic water flow. Inhibition of
prostaglandin synthesis caused luminal membrane water permeability to
increase much more than expected from tissue permeability measurements. The
addition of a very low dose of antidiuretic hormone (ADH) (0.125 mU/ml)
during prostaglandin synthesis inhibition increased luminal membrane water
permeability to the same level as maximal stimulation with ADH, while
tissue water permeability failed to increase proportionately. The results
imply the presence of a regulatable barrier to water movement across toad
bladder that is distal to the luminal membrane and subject to control by
either prostaglandins or ADH.
