Effect of hyaluronidase on albumin diffusion in lung interstitium

Albumin diffusion measured in an isolated segment of rabbit lung interstiti um with a radioactive tracer (I-125-albumin) technique was independent of a lbumin concentration and similar to the free diffusion of albumin in water (Qiu et al, 1998. J Appl Physiol 85: 575-583). We studied the effect of hya luronidase on the diffusion of albumin, Isolated rabbit lungs were inflated with silicon rubber by way of airways and blood vessels, and two chambers were bonded to the sides of a similar to 0.5-cm thick slab enclosing a vess el with an interstitial cuff. One chamber was filled with 2 g/dl albumin so lution containing I-125-albumin and 0.02 g/dl hyaluronidase. Unbound I-125 was removed from the tracer by dialysis before use. The other chamber fille d with Ringer's solution was placed within a NaI(TI) scintillation detector , Diffusion of tracer was measured continuously for 120 h. Albumin diffusio n coefficient (D) and interstitial area (A) were obtained by fitting the tr acer-time curve with the theoretical solution of the equation describing on e-dimension diffusion of a solute across a membrane. D averaged 5.2 x 10(-7 ) cm(2)/s for albumin diffusion with hyaluronidase, 20% less than that meas ured previously without hyaluronidase. Hyaluronidase had no effect on A. Re sults indicated an interaction between albumin and interstitial hyaluronan that was the opposite of the steric effect on albumin excluded volume measu red in solution.