Journal of Applied Physiology, Vol 58, Issue 6 2011-2019, Copyright © 1985 by American Physiological Society
Development of beta-adrenergic control of phospholipid secretion in rabbit lung
A. J. Corbet, H. W. Kolni, T. Perreault, J. A. Frink and A. J. Rudolph
Lung distension is associated with increased phospholipid secretion into
the air spaces. Basal, lavage-induced, and inflation-produced phospholipid
secretion, in postmortem in situ lungs of newborn rabbits, were examined at
three different levels of maturity, with and without 10(-3) M
dl-propranolol. Lungs were lavaged with saline at successive 3- and 15-min
time intervals to separate basal from lavage-induced secretion.
Inflation-produced secretion was studied after static inflation at 30 cmH2O
for 30 min. At 27.5 days gestation, basal secretion was undetectable, and
neither lavage-induced nor inflation-produced secretion were influenced by
propranolol. At 29.5 days gestation, basal secretion was only just
detectable. Distension-associated secretion was increased over that present
at 27.5 days gestation, and propranolol had a significant inhibitory
effect, especially on lavage-induced secretion, in which the inhibition was
shown to be rapidly reversible. There was a significant increase of basal
secretion at 2.5 days postterm, possibly inhibited by propranolol. In
addition, there was a further substantial increase of distension-associated
secretion, and the inhibitory effect of propranolol persisted. These
changes were independent of the sedimentation behavior of lavaged
phospholipid. Overall, the results are consistent with evidence, produced
in other laboratories, that there is an increasing density of sympathetic
neurons and beta-adrenergic receptors in whole lung preparations during
late gestation in the rabbit and suggest that granular pneumocytes, the
presumed source of secreted phospholipid, take part in this developmental
change.
