ALVEOLAR LIQUID CLEARANCE IN THE ANESTHETIZED VENTILATED GUINEA-PIG

Alveolar liquid clearance was examined in ventilated, anesthetized gui nea pigs. An isosmolar 5% albumin solution was instilled into the lung s. Alveolar liquid clearance was studied over 1 h and was measured fro m the increase in alveolar protein concentration as water was reabsorb ed. Basal alveolar liquid clearance was 38% of instilled volume. The h igh basal alveolar liquid clearance was not secondary to endogenous ca techolamine release. Compared with control animals, epinephrine and th e general beta-adrenergic agonist isoproterenol increased alveolar liq uid clearance to similar to 50% of instilled volume (P < 0.05), wherea s the beta(2)-adrenergic agonist terbutaline was without effect. The s timulation of alveolar liquid clearance by epinephrine or isoprotereno l was completely inhibited by the addition of the general beta-adrener gic inhibitor propranolol or the beta(1)-adrenergic inhibitor atenolol . Alveolar liquid clearance was inhibited by the sodium-channel inhibi tor amiloride by 30-40% in control animals and in animals treated with epinephrine or isoproterenol. Isoproterenol and epinephrine, but not terbutaline, increased adenosine 3',5'-cyclic monophosphate in in vitr o incubated lung tissue. The results suggest that alveolar liquid clea rance in guinea pigs is mediated partly through amiloride-sensitive so dium channels and that alveolar liquid clearance can be increased by s timulation of primarily beta(1)-adrenergic receptors.