Abstract
Objective:To measure the diffusion coefficient of albumin through rabbit mesentery using the steady-state flux of radioactive tracer 125I-albumin. The effect of albumin concentration and testicular hyaluronidase were also studied. Methods:Mesenteric tissue was bonded between two plates, exposing a 7 mm diameter surface, with two chambers on either side. One chamber was filled with a test solution of albumin containing the radioactive tracer and the other with lactated Ringer solution. The solutions in both chambers were stirred with small magnetic cylinders. The chamber filled with lactated Ringer solution was placed in a well-type NaI(Tl) detector, and the radiation emitted from the tracer that diffused across the mesentery was monitored continuously for 9 hours. The diffusion coefficient (D) was calculated using Fick's law of diffusion. The diffusion coefficient was measured at albumin concentration differences (ΔC) between ∼0 and 10 g/dL. The diffusion coefficient was also measured with testicular hyaluronidase at three different albumin-concentration differences. Results:The diffusion coefficient increased significantly (P< 0.0001) ∼ threefold from a mean value of 2.2 × 10−8± 1.2 × 10−8(SD) cm2/s at 0–0.5 g/dL ΔC to 5.9 × 10−8± 1.1 × 10−8(SD) cm2/s at 10 g/dL ΔC. The values are much less than the free diffusion coefficient of albumin (6 × 10−7cm2/s). Testicular hyaluronidase added to the albumin solution decreased D by ∼ 60%, but did not eliminate the increase in D with ΔC. Conclusions:The increase in D with ΔC and the reduced D with hyaluronidase were attributed to a reduced albumin-excluded volume caused by an interaction between albumin and hyaluronan. Further studies are required to define this interaction.