Water and Electrolytes of Rat Lung: Effects of Fluid-Filling, Perfusion, and Metabolic Inhibitor Treatment

Abstract

The left lobe of the rat lung was filled through the bronchus with Krebs Bicarbonate Ring-er solution (KBR) with 70,000 mol wt 14C-dextran. Electrolytes and water in slices of the lobe were measured. The volume of liquid trapped in the airspace estimated from the volume of distribution of dextran was equivalent to the gravimetrically determined difference in water content (1.2 1/kg dry wt or 21% of slice water) between slices of gas and KBR-filled lobes. Additional Na+ and Cl− in slices of liquid-filled lobes were accounted for by the NaCl in a volume of KBR equal to the volume of residual airspace fluid. Perfusion of liquid-filled lobes with KBR with 6% colloid for 1 hr did not affect tissue water (4.4 1/kg dry wt), electrolytes (Na+ = 406, K+ = 336, Cl− = 388 mEq/kg dry wt) or Q02 (7 μl/mg dry wt., hr). The permeability coefficient for dextran movement between the airspace and perfusion fluid was 6 × 10−10 cm/sec. The tissue compartment of slices from lobes perfused with 1% colloid in KBR was 22% larger. Na+ and Cl− increased but K+ and Pdextran were unchanged. These results suggest the formation of interstitial edema. Addition of ouabain (10−3M) or NaCN and iodoacetamide (10−3M each) to the perfusion fluid resulted in the loss of about 150 mEq/kg dry wt of tissue K+ and a gain of an equal amount of Na+. Tissue Cl− and water did not change. Exchange of Na+ for cell K+ is suggested. We conclude that the slice technique can be used to monitor changes in the composition and volume of liquid compartments of the parenchyma of liquid-filled lungs.