Effect of hyaluronidase on interstitial cuff and pressure response in liquid-inflated rabbit lung

The sequential pattern of perivascular interstitial cuff growth was studied in liquid-inflated rabbit lungs. Degassed isolated lungs were immersed in a saline bath and inflated to 5 cmH2O transpulmonary pressure with a 3% albumin solution or 3% albumin solution containing hyaluronidase. After inflation times varying between 1 and 7 h, the lungs were frozen in liquid N2. From blocks cut from the frozen lungs, interstitial cuff cross-sectional area was measured as a function of vessel size. No cuffs were observed around vessels less than 0.1 mm diam. At all inflation times, only approximately 50% of vessels less than 0.5 mm diam had cuffs, whereas virtually all vessels greater than 0.5 mm diam had cuffs. Cuff-to-vessel area ratio increased with inflation time, reaching a maximum of 1.0-1.4 by 5 h. The time constant of cuff growth was 1 h for the albumin-inflated lungs and was independent of vessel size. The time constant was reduced by 60% in the hyaluronidase-inflated lungs. The time constant for the response in perivascular interstitial pressure measured by micropuncture near the lung hilum was 2.5 h for albumin-inflated lungs and 1.2 h for hyaluronidase-inflated lungs. Electrical analog models were used to fit the experimental data of cuff growth and to determine interstitial liquid resistance. Interstitial resistance for the albumin-inflated rabbit lungs was 2- and 24-fold greater than values estimated previously for sheep and dog lungs, respectively.