Journal of Applied Physiology, Vol 77, Issue 2 507-516, Copyright © 1994 by American Physiological Society
Developmental differences in vascular responses to hypoxia in lungs of rabbits
C. D. Fike and M. R. Kaplowitz
Department of Pediatrics, University of Utah Medical Center, Salt Lake City 84132.
Our purpose was to determine whether postnatal age and prostaglandins
influence the sites of hypoxic vasoconstriction in lungs of rabbits. To do
this, we used the micropuncture technique to measure pressures in 20- to
80-microns-diam subpleural arterioles and venules during sequential
inflation of lungs of newborn and adult rabbits with normoxic (21% O2-7-10%
CO2-69-72% N2) and hypoxic (90-93% N2-7-10% CO2) gas mixtures. Indomethacin
(40 micrograms/ml) was added to the perfusate of some lungs of each age
group. During hypoxia in untreated lungs of newborn rabbits, both pulmonary
arterial and 20- to 80-microns-diam arteriolar pressure increased by 5%,
whereas 20- to 80-microns-diam venular pressure remained the same. In
contrast, during hypoxia in untreated lungs of adult rabbits, pulmonary
arterial pressure increased by 48%, whereas 20- to 80-microns-diam
arteriolar pressure decreased slightly and 20- to 80-microns-diam venular
pressure did not change. Regardless of the presence of indomethacin,
location of vessels used for micropuncture, or level of left atrial
pressure, pulmonary arterial pressure was the only measured vascular
pressure that increased with hypoxia in adult lungs. Thus, in adult lungs,
the site of hypoxia-induced vasoconstriction was limited to arteries >
80 microns diam, whereas in newborn lungs the site of hypoxia-induced
vasoconstriction included vessels both larger and smaller than 20- to
80-microns-diam arteries. This age-related difference in the sites of
hypoxia-induced vasoconstriction was not found in indomethacin-treated
lungs.
