TIME-COURSE OF ACTIVE AND PASSIVE LIQUID AND SOLUTE MOVEMENT IN THE ISOLATED-PERFUSED RAT LUNG MODEL

The isolated perfused rat lung model (IL) is used to study alveolar ep ithelial transport properties. Most of the previous studies have been done over a short period of time and have not used the same preparatio n as a control and intervention group. We evaluated whether the IL pre paration could be used for a prolonged period of time (5 h) and studie d the rates of active Na+ transport, lung liquid clearance, and passiv e movement of solutes. Active Na+ transport and lung liquid clearance were stable from 1 to 5 h. The passive movement of small solutes (Na+, mannitol) did not change significantly, and albumin movement increase d slightly at the fifth hour. Total RNA isolated from IL after 5 h was intact, and the Na+-K+-ATPase activity in alveolar type II cells isol ated at the end of 5-h experiments was equal to Na+-K+-ATPase function from freshly isolated alveolar type II cells. Finally, we measured th e stimulatory effect of the beta-adrenergicagonist terbutaline and the inhibitory effect of the Na+-K(+)ATPase-antagonist ouabain by using t he same animal as a control. Accordingly, the isolated perfused lung m odel is functionally stable for at least 5 h, and it could be utilized to evaluate the effect of different interventions by using the same p reparation.