EFFECT OF HYDRATION ON LUNG INTERSTITIAL CONDUCTIVITY RESPONSE TO ELECTRICALLY CHARGED SOLUTIONS

In interstitial segments of rabbit lung, we compared the flow of a sol ution containing cationic protamine sulfate (0.08 mg/ml) or cationic d extran (0.1%) to that of Ringer or neutral dextran solution. Also comp ared, were the flow of solutions containing anionic dextran (0.1 or 1. 5%) to those containing neutral dextran and the flow of hyaluronidase solution (0.02%) to that of Ringer solution, at mean interstitial pres sures (Pm) between -5 and 15 cmH(2)O. Driving pressure was set at 5 cm H(2)O. Cationic protamine or cationic dextran-to-Ringer flow ratio inc reased with Pm (presumably as hydration increased) but in nonedematous interstitium (-5 cmH(2)O Pm), flow ratio was 1, indicating a viscosit y-dependent flow. In contrast, the flow of anionic dextran solution de creased relative to that of neutral dextran; this decrease was constan t with hydration, but was greater at the higher concentration of dextr an. Interstitial conductivity to the flow of hyaluronidase increased w ith hydration. However, this behavior was absent after the flow of 1.5 % anionic dextran, indicating an inhibitory effect of the higher conce ntration of anionic dextran on the hyaluronidase response. A negative charge in microvascular filtrate may control fluid clearance in normal interstitium, while a positive charge would enhance clearance only in edema formation. (C) 1997 Elsevier Science B.V.