Protein composition of lung fluids in acute alloxan edema in dogs

Abstract

In 11 anesthetized dogs with acute alloxan-induced pulmonary edema, we measured the protein composition of 1-mul samples of plasma, free interstitial fluid, alveolar fluid, and airway fluid. We obtained plasma and airway fluid at regular intervals as edema developed. We sampled alveolar fluid by pleural micropuncture in the unfrozen, excised lung and free interstitial fluid from perivascular cuffs in the frozen, excised lung. The average (+/- 1 SD) total protein concentration of plasma was 4.9 +/- 0.6, airway fluid 4.4 +/- 0.7, free interstitial fluid 4.9 +/- 0.7, and alveolar fluid 5.2 +/- 0.8 g/100 ml. The average fractions of albumin were 0.42 +/- 0.05, 0.50 +/- 0.05, 0.49 +/- 0.06, and 0.49 +/- 0.07, respectively. By paired analysis, the protein concentration of interstitial fluid was not significantly different from alveolar fluid. The protein concentration of airway fluid was significantly less than that in interstitial and alveolar fluid. The albumin fraction of the three lung fluids was identical but significantly different from plasma. We conclude that in alloxan-induced pulmonary edema the lung fluids contain high concentrations of protein and the alveolar epithelial membrane becomes freely permeable to protein molecules.

Alveolar epithelial damage. A critical difference between high pressure and oleic acid-induced low pressure pulmonary edema.

“…Vreim et al (3) showed that in high pressure pulmonary edema, with the extravascular lung water-to-dry weight ratio ranging from 6.6 to 15.7, the alveolar flooding was less obvious. However, they had much less difficulty producing alveolar flooding in low pressure pulmonary edema (2). A recent study by Julien et al (19) shows that the amount of lung water present in low pressure pulmonary edema may have been underestimated by expressing it per gram of bloodfree dry tissue.…”

“…In a subsequent study Vreim and Staub (2) also showed that in alloxaninduced low pressure pulmonary edema (LPPE),1 alveolar flooding occurs more readily and the fluid has a higher protein content and an increased number of cells compared with high pressure pulmonary edema (HPPE) (3). These observations suggest that epithelial permeability may be quite different under the two conditions, and this is supported by the observations that HPPE clears rapidly with therapy (4) compared with LPPE, which takes days to resolve (5).…”

High permeability pulmonary edema (ARDS) during tocolytic therapy — a case report

“…Animal studies in which alveolar fluid was obtained by direct alveolar micropuncture have shown that the protein concentration of alveolar fluid is similar to that of fluid in the airways in both cardiac and permeability types of pulmonary edema [19,20]. Clinical studies have shown that the analysis of edema protein relative to plasma protein concentrations is useful in separating these two types of pulmonary edema.…”

Noninvasive measurement of pulmonary transvascular protein flux in normal man.

“…In typical "cardiogenic" pulmonary edema, recruitment of capillary bed results in an increased surface area available for macromolecular flux, whereas an increase in convective forces leads to greater flux per unit surface area (2)(3)(4). In "noncardiogenic" pulmonary edema, a "capillary-leak syndrome," with impairment of the normal molecular sieving function of the endothelial membrane, results in veritable "flooding" of the interstitium with oncotically active proteins (5)(6)(7). Clinical measurement of transvascular protein flux in lung may aid in early diagnosis of pulmonary edema, and allow differentiation between "cardiogenic" and "noneardiogenic" types based on the magnitude of detected changes.…”