Asymmetric ( UC)albumin transport across bullfrog alveolar epithelium

Journal Article · Tue Oct 01 00:00:00 EDT 1985 · J. Appl. Physiol.; (United States)

OSTI ID:6287515

Kim, K J; LeBon, T R; Shinbane, J S; Crandall, E D

Bullfrog lungs were prepared as planar sheets and bathed with Ringer solution in Ussing chambers. In the presence of a constant electrical gradient (20, 0, or -20 mV) across the tissue, UC-labeled bovine serum albumin or inulin was instilled into the upstream reservoir and the rate of appearance of the tracer in the downstream reservoir was monitored. Two lungs from the same animal were used to determine any directional difference in tracer fluxes. An apparent permeability coefficient was estimated from a relationship between normalized downstream radioactivities and time. Results showed that the apparent permeability of albumin in the alveolar to pleural direction across the alveolar epithelial barrier is 2.3 X 10(-7) cm/s, significantly greater (P less than 0.0005) than that in the pleural to alveolar direction (5.3 X 10(-8) cm/s) when the tissue was short circuited. Permeability of inulin, on the other hand, did not show any directional dependence and averaged 3.1 X 10(-8) cm/s in both directions. There was no effect on radiotracer fluxes permeabilities of different electrical gradients across the tissue. Gel electrophoretograms and corresponding radiochromatograms suggest that the large and asymmetric isotope fluxes are not primarily due to digestion or degradation of labeled molecules. Inulin appears to traverse the alveolar epithelial barrier by simple diffusion through hydrated paracellular pathways. On the other hand, ( UC)albumin crosses the alveolar epithelium more rapidly than would be expected by simple diffusion. These asymmetric and large tracer fluxes suggest that a specialized mechanism is present in alveolar epithelium that may be capable of helping to remove albumin from the alveolar space.

• Research Organization: Univ. of California, Los Angeles
• OSTI ID: 6287515
• Journal Information: J. Appl. Physiol.; (United States), Vol. 4
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ALBUMINS
MEMBRANE TRANSPORT
EPITHELIUM
PERMEABILITY
INULIN
CARBON 14 COMPOUNDS
DIFFUSION
FROGS
LUNGS
AMPHIBIANS
ANIMAL TISSUES
ANIMALS
AQUATIC ORGANISMS
BODY
CARBOHYDRATES
LABELLED COMPOUNDS
ORGANIC COMPOUNDS
ORGANS
POLYSACCHARIDES
PROTEINS
RESPIRATORY SYSTEM
SACCHARIDES
TISSUES
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques