EFFECT OF HYDRATION ON LUNG INTERSTITIAL PERMEABILITY RESPONSE TO ALBUMIN AND HYALURONIDASE

Previous studies showed that the flows of albumin and hyaluronidase so lutions increased relative to that of saline in isolated segments of r abbit 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 i nterstitial pressures (P-m) between -5 and 15 cmH(2)O with a constant driving pressure of 5 cmH(2)O. The albumin-to-Ringer flow ratio increa sed monotonically from near the viscosity-dependent value (0.75-0.77) at -5 cmH(2)O P-m to values of 1.6-2.1 at 15 cmH(2)O P-m. A similar be havior was observed for the flow of the hyaluronidase solution relativ e to that of Ringer solution. The increased permeability response to a lbumin was independent of the albumin concentration used. By contrast, the response to hyaluronidase was lower when the interstitium was per fused with the higher concentration albumin solution (10 g/dl) before the flow of hyaluronidase, indicating an inhibitory effect of albumin on the hylauronidase response. Estimates of interstitial hydration fro m P-m indicated an increased interstitial permeability (conductivity) to the flows of albumin and hyaluronidase solutions only after interst itial volume had doubled, whereas interstitial permeability was viscos ity dependent at normal interstitial hydration.