DIFFERENCES IN SODIUM AND D-GLUCOSE TRANSPORT BETWEEN HAMSTER AND RATLUNGS

The purpose of this study was to characterize phloridzin- and amilorid e-sensitive transport across blood-gas barrier of hamster and rat lung s. Air spaces of isolated perfused lungs were instilled with a solutio n containing Na-22 or L-[H-3]glucose, D-[C-14]glucose, and fluorescein isothiocyanate-labeled dextran. Apparent permeability-surface area pr oducts (PS) were calculated. Phloridzin (Na+-dependent D-glucose trans port inhibitor) had no effect on D-glucose or sodium transport out of air spaces in hamster lungs. In contrast, in rat lungs, phloridzin dec reased PS for D-glucose by 89% and that for Na by 28%. Trapping of (CO 2)-C-14 in vascular samples was measured to estimate metabolism. Unlab eled air space D-glucose increased appearance of perfused D-[C-14]gluc ose in air spaces of rat lungs. We conclude that Na+-dependent D-gluco se transport is important for D-glucose uptake in rat lungs but not in hamster lungs. In hamster lungs, amiloride (Na+ transport inhibitor) also decreased PS for sodium, but drugs known to stimulate sodium tran sport in rat lungs had no effect. Thus, species differences in active transport processes exist in the distal air spaces of mammalian lungs.