Journal of Applied Physiology, Vol 70, Issue 4 1677-1685, Copyright © 1991 by American Physiological Society
Functional assessment of pulmonary capillary surface area in the 2-mo-old lamb
B. R. Pitt, G. Lister, J. J. Perez Fontan and P. Davies
Department of Pharmacology, University of Pittsburgh School of Medicine, Pennsylvania 15261.
We recently reported that measurements of the maximal velocity of pulmonary
endothelial angiotensin-converting enzyme (Vmax) in vivo provide
information regarding microvascular surface area in the developing lamb. To
obviate any subtle influences of development on Vmax aside from simple
increases in surface area, we correlated Vmax with postmortem stereological
assessments of alveolar surface area in the relatively mature lung of the
2-mo-old lamb (n = 14). We attempted to increase the range of surface area
beyond its normal variability by injecting nine of the lambs with
bleomycin, an antineoplastic agent with significant pulmonary toxicity in
other species. Vmax, measured shortly after birth and then weekly,
increased monotonically in all lambs. Despite their wide dispersion, Vmax
and the stereological determinations correlated strongly at 2 mo of age,
confirming that Vmax is a robust indicator of the surface area of the
air-blood barrier. There was no significant difference in either
measurement between the control lambs and those treated with bleomycin,
suggesting that the newborn lamb is resistant to the effect of this agent.
