Journal of Applied Physiology, Vol 45, Issue 4 516-520, Copyright © 1978 by American Physiological Society
Fibrinogen clearance from alveoli
E. C. Meyer, R. Ottaviano and J. J. Higgins
In experiments lasting 311 +/- 8 (SE) min, we studied the clearance of
125I-fibrinogen ([125I])RIF) from distal lung units of anesthetized,
ventilated dogs. We instilled varying concentrations of isosmolar, citrated
[125I]RIF ranging from 0.75 to 4 mg/ml into alveoli of individual dogs, and
we monitored clearance by the use of external detectors and blood and lymph
sampling. Approximately 9% [125I]RIF passed into proximal airways according
to detector signal analysis. Excluding airway flow, whole lung clearance of
[125I]RIF occurred by degradation to small molecules that rapidly became
evenly distributed in body extracellular water. The degradation appeared to
take place within the distal airway and not within the lung interstitium
because 131I-fibrinogen, injected intravenously, was degraded less in
passing from plasma to right duct lymph. The intra-alveolar kinetics of
[125I]RIF had 1.5 reaction order with a specific rate of 1.27 X 10(-5)
ml(3/2)-mg(-1/2)-min(-1). The data indicate that fibrinogen clearance from
alveoli occurs by both transbronchial bulk flow and intraalveolar
degradation.
