Journal of Applied Physiology, Vol 51, Issue 2 306-312, Copyright © 1981 by American Physiological Society
Surface activity following natural surfactant treatment in premature lambs
M. Ikegami, A. Jobe and T. Glatz
Premature lambs with respiratory failure [CO2 partial pressure (PCO2)
greater than 70 Torr] were treated with 50 mg/kg 3H-labeled natural
surfactant by tracheal instillation. Minimum surface tensions of sequential
samples suctioned from the airways fell from 25 +/- 3 dyn/cm before
treatment to 8 +/- 5 dyn/cm after treatment and again rose to 32 +/- 2
dyn/cm at death. Minimum surface tensions of alveolar wash samples taken at
death were 27 +/- 4 dyn/cm, whereas surfactant fractions reisolated from
the alveolar washes lowered surface tension to under 10 dyn/cm. The
alveolar washes, surfactant reisolated from the alveolar washes, and
natural surfactant had similar phospholipid compositions; however, the
alveolar washes contained about 40 times more protein per micromole
phosphatidylcholine. The natural surfactant used for treatment apparently
was inactivated by an inhibitor of surfactant function. After intravenous
injections of [14C]palmitic acid, labeled saturated phosphatidylcholine
appeared on the airways, indicating endogenous synthesis and secretion.
However, the specific activity of the 3H-labeled saturated
phosphatidylcholine in the natural surfactant used for treatment decreased
by only 30 +/- 4% in the alveolar wash; thus the treatment dose was not
diluted to a large extent by endogenous pools.
