EQUILIBRATION OF INTRAVASCULAR ALBUMIN WITH LUNG LYMPH IN UNANESTHETIZED SHEEP

Abstract

In 16 unanesthetized sheep with chronic lung lymph fistulas we measured pulmonary vascular pressures, lymph flow,  lymph  and  plasma  total  protein and albumin concentration. We determined the rate of equilibration of radioiodinated albumin  between plasma and lung lnterstitial fluid (lung lymph) in three steady-state cond itions; baseline (n = 14), in­creased pulmonary  microvascular pressure  (n = 9) and increased microvascular permeability  (n = 4). The tracer protein equilibration  proceeded according to single compartment wash-in kinetics in all experiments. Lung lymph flow averaged 5.3 ± 2.8 (S.D.) ml/ h  under baseline  conditions,  16. l  ± 10.6  ml/h during increased pressure and  37.3 ± 29.4 ml/h during increased permeability. The half time of equilibration averaged 2.9 ± 1.0 h, 2. 2 ± 1.0 h ind 0.7 ± 0.2 h, respectively. Lung interstitial fluid equilibrates with  plasma  proteins more  rapidly  than most other organs. The marked difference between m creased permeability and the other conditions de­monstrates the sensi- tivity of this method. No evi­dence was obtained that  any  tracer  protein  entered lung lymph within the caudal mediastinal lymph

node.