AJP - Regulatory, Integrative and Comparative Physiology, Vol 238, Issue 5 395-R399, Copyright © 1980 by American Physiological Society
Age-related differences in angiotensin I metabolism by isolated perfused rat lungs
K. B. Wallace, R. A. Roth, J. B. Hook and M. D. Bailie
The pulmonary vasculature has been implicated in the clearance of several
vasoactive substances from the circulation including angiotensin I (AI). In
view of the previously reported age-related differences in
angiotensin-converting enzyme (ACE) activity of lung homogenates, it was of
interest to examine the ability of intact perfused lungs to metabolize AI.
Lungs from newborn and adult rats were perfused with Krebs bicarbonate
buffer containing 1.0 ng/ml AI in a single-pass, nonrecirculating system.
The rate of perfusion was normalized to lung mass. Removal of AI was
determined from the transpulmonary difference in radioimmunoassayable AI.
Lungs from 7-day-old rats removed a smaller fraction of AI from the
circulation than did adult lungs. The age-related increase in AI clearance
was accompanied by an increase in pulmonary ACE content; however, enzyme
content alone could not account for the observed differences. The increased
metabolism of AI by the pulmonary vasculature during development may
contribute to the age-related increase in circulating angiotensin II
concentrations.
