Effect of hydration on lung interstitial permeability response to albumin and hyaluronidase

Previous studies showed that the flows of albumin and hyaluronidase solutions increased relative to that of saline in isolated segments of rabbit lung interstitium (Lai-Fook et al. J. Appl. Physiol. 67:606-613, 1989). We questioned whether these effects were hydration dependent. In interstitial segments the flows of lactated Ringer, albumin (5 and 10 g/dl), and hyaluronidase (0.02%) solutions were measured at mean interstitial pressures (Pm) between -5 and 15 cmH2O with a constant driving pressure of 5 cmH2O. The albumin-to-Ringer flow ratio increased monotonically from near the viscosity-dependent value (0.75-0.77) at -5 cmH2O Pm to values of 1.6-2.1 at 15 cmH2O Pm. A similar behavior was observed for the flow of the hyaluronidase solution relative to that of Ringer solution. The increased permeability response to albumin was independent of the albumin concentration used. By contrast, the response to hyaluronidase was lower when the interstitium was perfused with the higher concentration albumin solution (10 g/dl) before the flow of hyaluronidase, indicating an inhibitory effect of albumin on the hyaluronidase response. Estimates of interstitial hydration from Pm indicated an increased interstitial permeability (conductivity) to the flows of albumin and hyaluronidase solutions only after interstitial volume had doubled, whereas interstitial permeability was viscosity dependent at normal interstitial hydration.