TY - JOUR
T1 - The water permeability of toad urinary bladder
T2 - I. Permeability of Barriers in Series with the Luminal Membrane
AU - Levine, Sherman D.
AU - Jacoby, Monica
AU - Finkelstein, Alan
PY - 1984/4/1
Y1 - 1984/4/1
N2 - Antidiuretic hormone (ADH) induces a large increase in the water permeability of the luminal membrane of toad urinary bladder. Measured values of the diffusional water permeability coefficient, Pd(w), are spuriously low, however, because of barriers within the tissue, in series with the luminal membrane, that impede diffusion. We have now determined the water permeability coefficient of these series barriers in fully stretched bladders and find it to be ~6.3 × 10-4 cm/s. This is equivalent to an unstirred aqueous layer of ~400 µm. On the other hand, the permeability coefficient of the bladder to a lipophilic molecule, hexanol, is ~9.0 × 10-4 cm/s. This is equivalent to an unstirred aqueous layer ofonly 100 jam. The much smaller hindrance to hexanol diffusion than to water diffusion by the series barriers implies a lipophilic component to the barriers. We suggest that membrane-enclosed organelles may be so tightly packed within the cytoplasm of granular epithelial cells that they offer a substantial impediment to diffusion of water through the cell. Alternatively, the lipophilic component of the barrier could be the plasma membranes of the basal cells, which cover most of the basement membrane and thereby may restrict water transport to the narrow spaces between basal and granular cells.
AB - Antidiuretic hormone (ADH) induces a large increase in the water permeability of the luminal membrane of toad urinary bladder. Measured values of the diffusional water permeability coefficient, Pd(w), are spuriously low, however, because of barriers within the tissue, in series with the luminal membrane, that impede diffusion. We have now determined the water permeability coefficient of these series barriers in fully stretched bladders and find it to be ~6.3 × 10-4 cm/s. This is equivalent to an unstirred aqueous layer of ~400 µm. On the other hand, the permeability coefficient of the bladder to a lipophilic molecule, hexanol, is ~9.0 × 10-4 cm/s. This is equivalent to an unstirred aqueous layer ofonly 100 jam. The much smaller hindrance to hexanol diffusion than to water diffusion by the series barriers implies a lipophilic component to the barriers. We suggest that membrane-enclosed organelles may be so tightly packed within the cytoplasm of granular epithelial cells that they offer a substantial impediment to diffusion of water through the cell. Alternatively, the lipophilic component of the barrier could be the plasma membranes of the basal cells, which cover most of the basement membrane and thereby may restrict water transport to the narrow spaces between basal and granular cells.
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U2 - 10.1085/jgp.83.4.529
DO - 10.1085/jgp.83.4.529
M3 - Article
C2 - 6726173
AN - SCOPUS:0021238823
SN - 0022-1295
VL - 83
SP - 529
EP - 541
JO - Journal of General Physiology
JF - Journal of General Physiology
IS - 4
ER -