Journal of Applied Physiology, Vol 72, Issue 1 29-38, Copyright © 1992 by American Physiological Society
Evaluating flux of labeled albumin into the pulmonary interstitium of sheep lungs
W. R. Riddle, R. J. Roselli, R. E. Parker and N. A. Pou
Department of Radiology and Radiological Sciences, School of Medicine, Vanderbilt University, Nashville, Tennessee 37235.
A noninvasive method was used to measure the movement of 131I-labeled
albumin across the pulmonary microvascular barrier of a blood-perfused in
situ sheep lung lymph preparation. After injection of labeled albumin into
the blood, external measurements of gamma activity were taken for 2 h. The
interstitial concentrations were calculated by applying the external
activities and sampled lung lymph concentrations to a mass transport model.
For the external activities and lymph activities to yield the same
quantitative results, two modifications were necessary. First, lymph
concentrations were corrected for transport delay from the lymphatic
system. Second, externally detected radioactivity had to be corrected for
the contribution of unbound nuclide. Application of a mathematical model to
the data indicated the extravascular distribution volume for albumin was
79% of the pulmonary blood volume, and the extravascular distribution
volume for radiolabeled iodide was 4.42 times greater than the pulmonary
blood volume. The permeability-surface area product for iodide in the lung
was estimated to be 0.274 ml.min-1.g blood-free dry lung wt-1. The
transport delay in the lymphatic system was approximately 30-45 min and
represented a volume of 1.44-2.80 ml.
