Permeability of dog lung endothelium to sodium, diols, amides, and water.

Bolus injection of T-1824-albumin, test indicator, and tritiated water into a jugular vein of the anesthetized dog and sequential sampling of blood from a carotid artery yielded multiple-indicator outflow patterns for the lung. Permeability-surface products of the test indicator for the lung endothelial barrier were obtained by comparison of test indicator with T-1824-albumin on the upslope of the test-indicator curve and correction for backdiffusion. The derived endothelial permeability coefficients, based on surface area/wet lung weight-500 cm2/g (mean +/- 2 SE, 10(-5) cm s(-1)), were: sodium ion, 2.9 +/- 0.8; ethylene glycol, 7.3 +/- 1.5; 1, 3-propranediol, 7.9 +/- 3.2; 1, 2-propanediol, 10 +/- 4; 1, 4-butanediol, 14 +/- 8; 1, 5-pentanediol, 21 +/- 6; 1, 6-hexanediol, 41 +/- 11; formamide, 16 +/- 9; acetamide, 13 +/- 4; propionamide, 31 +/- 12; butyramide, 42 +/- 24; valeramide, 79 +/- 12; tritiated water, 150 +/- 50. The backdiffusion correction varies from 8% for sodium to 75% for valeramide. A parallel-pathway model of blood-tissue passive exchange of small nonelectrolyte solutes is compatible with these results, with a lipid pathway through endothelial cells and an aqueous pathway possibly through interendothelial clefts.