Journal of Applied Physiology, Vol 56, Issue 1 72-77, Copyright © 1984 by American Physiological Society
Effects of cell swelling on fluid flow across alveolar epithelium
J. D. Schaeffer, K. J. Kim and E. D. Crandall
The effects of decreased temperature, metabolic inhibition, and
hyposmolality on osmotically and hydrostatically driven water flux across
bullfrog alveolar epithelium were studied. Lungs were isolated from
double-pithed Rana catesbeiana and prepared as sacs. Either an osmotic (0.1
M raffinose) or hydrostatic (6.3-6.6 Torr) pressure gradient was imposed
across the tissue. These gradients resulted in the volume flow of water
from the alveolar to pleural bath. Control water flux and hydraulic
conductivity were estimated from the rate of weight loss of the lung sac.
Subsequently water flux and hydraulic conductivity were determined under
one of the following conditions: 1) temperature of bathing solutions
lowered to 2 degrees C; 2) 1 mM 2,4-dinitrophenol added to both alveolar
and pleural baths, or 3) both baths changed to half-isosmotic Ringer
solution. The control hydraulic conductivities for osmotic (Lpo) and
hydrostatic (Lph) pressure gradients were 3.65(+/- 0.94) X 10(-12) and
2.14(+/- 0.63) X 10(-10) ml/dyn X s, respectively. Under conditions of
metabolic inhibition, hyposmolality, and decreased temperature, Lph
decreased by 77, 83, and 92%, and Lpo decreased by 56, 34, and 59%,
respectively. These results are most consistent with the hypothesis that
the decrements in hydraulic conductivity under our experimental conditions
are due to epithelial cell swelling and perhaps to changes in the
characteristics of the paracellular pathway.
