Impairment of transalveolar fluid transport and lung Na+-K+-ATPase function by hypoxia in rats

We examined whether hypoxic exposure in vivo would influence transalveolar fluid transport in rats. We found a significant decrease in alveolar fluid clearance of the rats exposed to 10% oxygen for 48 h. Terbutaline did not s timulate alveolar fluid clearance, and alveolar fluid cAMP levels were lowe r than those determined in normoxia experiment. Hypoxia did not influence t he alveolar fluid lactate dehydrogenase levels, Evans blue dye fluid-to-ser um concentration ratio, or lung wet-to-dry weight ratio, indicating no sign ificant change in the permeability of alveolar-capillary barrier Histologic al examination showed no significant fluid accumulation into the interstiti um and the alveolar space. Hypoxia did not reduce lung ATP content; however , we found significant decrease in Na+-K+-ATPase hydrolytic activity in lun g tissue preparations and isolated alveolar type II cells. Our data indicat e that hypoxic exposure in vivo impairs transalveolar fluid transport, and this impairment is related to the decrease in alveolar epithelial Na+-K+-AT Pase hydrolytic activity but is not secondary to the alteration of cellular energy source.