Journal of Applied Physiology, Vol 52, Issue 3 792-797, Copyright © 1982 by American Physiological Society
Extravascular, extracellular water in rabbit lung using Na and sucrose indicators
D. J. Pavlin, R. H. Haschke, M. L. Nessly and F. W. Cheney Jr
We compared the volume of the pulmonary extravascular, extracellular water
space using sodium and sucrose indicators in 8 normal and 11 edematous
rabbit lungs by steady-state techniques. The volume of the extravascular,
extracellular space (EVECW), expressed in milliliters per gram dry lung,
was determined from the volume of distribution of 24Na, [3H]sucrose, or
total sodium in 1) supernatant solutions obtained by centrifugation of
homogenized lung or 2) intact lung fragments. There was no significant
difference in EVECW measured in normal lungs [24Na 1.88 +/- (SD) 0.31;
[3H]sucrose 1.84 +/- (SD) 0.27] or edematous lungs [24Na 4.78 +/- (SD)
1.44; [3H]sucrose 4.41 +/- (SD) 1.33] when comparing supernate solutions of
homogenized lungs. Similarly, there was no significant difference between
the volumes of distribution (EVECW) of these two isotopes when measured in
intact fragments of normal lung [24Na 2.08 +/- (SD) 0.28; [3H]sucrose 1.68
+/- (SD) 0.37]. The volume of EVECW measured in supernates was less than in
fragments with both isotopes. Washing the centrifuged tissue pellet and
adding the wash activity to the initial supernate activity yielded results
that were equal to the fragment technique. The failure to detect
significant differences between 24Na and [3H]sucrose spaces in the lung
suggests that the contribution on intracellular sodium to the measurement
of lung water is small and relatively insignificant, at least within the
confines of this experiment.
