A pore transport model for pulmonary alveolar epithelium.
Hydrodynamic heteropore flow models for transport of solutes across alveolar epithelial tissue have been developed. A two-size cylindrical pore model and a similar parallel-plate model were formulated, tested and used to predict effective pore sizes from literature data on transport in bullfrog, canine and rat lungs. The best fit equivalent pore-size estimates were obtained using a modified, nonlinear least squares procedure, with alveolar surface area to volume ratio (S/V) and small-pore area fraction of total pore area as parameters. Small-pore and large-pore width estimates of 4 nm (84% of total flow area) and 10 nm, respectively, with an average deviation of 20% from experimentally derived permeabilities were obtained from the bullfrog alveolar epithelium parallel-plate pore model (13 solutes, diameters 0.3 to 2.8 nm). The equivalent cylindrical pore model diameter estimates were 5 nm and 10 nm, with small-pore area fraction and percentage deviations similar to the parallel-plate model estimates. Eighty-eight percent of the bulk water driven by a sucrose osmotic gradient was predicted to be transported through the small pores. The rat alveolus parallel-plate pore model (6 solutes) yielded small-pore and large-pore widths of 0.4 nm and 50 nm, respectively. Clearance rate-constant data for dextran macromolecules (3,000 to 250,000 Daltons), using a single parallel-plate pore model, resulted in a pore width estimate of 98 nm for canine alveoli with an average deviation of the predicted rate constants of 18% from literature experimental values. In all cases tested, the parallel-plate pore model predicted lower small-pore size estimates than did the cylindrical pore model, and both models had appreciably smaller percentage deviations from experimental data than previous models.
Chandra
T
T
Department of Chemical Engineering, University of Illinois, Chicago 60612.
Miller
I F
IF
Yeates
D B
DB
D000818:Animals; D001692:Biological Transport; D002199:Capillary Permeability; D003911:Dextrans / Q000493:pharmacokinetics; D004058:Diffusion; D004285:Dogs; D004730:Endothelium, Vascular / Q000502:physiology; D004848:Epithelium / Q000502:physiology; D008954:Models, Biological; D008970:Molecular Weight; D010316:Particle Size; D011650:Pulmonary Alveoli / Q000502:physiology*; D051381:Rats; D012016:Reference Values
D003911:Dextrans