Effect of temperature on alveolar liquid and protein clearance in an in situ perfused goat lung.

To study the mechanisms of alveolar liquid and protein clearance, we investigated the effect of four different temperatures (7, 18, 30, and 38 degrees C) on the rate of liquid, [14C]mannitol, and 125I-labeled albumin (125I-albumin) transport from the air spaces of isolated perfused in situ goat lungs over 4 h under isogravimetric conditions. The concentrations of both native proteins and 125I-albumin in the alveolar fluid after 4 h were used to estimate alveolar liquid clearance. We instilled autologous serum (2 ml/kg) with 125I-albumin and [14C]mannitol into the distal air spaces of one lung and 131I-labeled albumin into the perfusate to measure the capillary-to-alveolar permeability to protein. Alveolar liquid clearance progressively declined from a control value of 24 +/- 6% at 38 degrees C to 12 +/- 7% at 30 degrees C, to 3 +/- 3% at 18 degrees C, and to -15 +/- 11% at 7 degrees C. 125I-albumin clearance into the perfusate was 0.3%/h of the instilled 125I-albumin at 38 degrees C. The clearance decreased abruptly to 0.06%/h at 30 degrees C and then slightly increased to 0.08%/h at 18 degrees C and to 0.15%/h at 7 degrees C. There were no changes in transport except for a twofold increase in mannitol at 7 degrees C. Increased permeability of the alveolar barrier to protein and small-molecular-weight tracers at 7 degrees C indicates that the barrier function of the alveolar epithelium is disrupted at this low temperature.(ABSTRACT TRUNCATED AT 250 WORDS)