Alveolar liquid clearance in the anesthetized ventilated guinea pig

Abstract

Alveolar liquid clearance was examined in ventilated, anesthetized guinea pigs. An isosmolar 5% albumin solution was instilled into the lungs. Alveolar liquid clearance was studied over 1 h and was measured from the increase in alveolar protein concentration as water was reabsorbed. Basal alveolar liquid clearance was 38% of instilled volume. The high basal alveolar liquid clearance was not secondary to endogenous catecholamine release. Compared with control animals, epinephrine and the general β-adrenergic agonist isoproterenol increased alveolar liquid clearance to ∼50% of instilled volume ( P < 0.05), whereas the β2-adrenergic agonist terbutaline was without effect. The stimulation of alveolar liquid clearance by epinephrine or isoproterenol was completely inhibited by the addition of the general β-adrenergic inhibitor propranolol or the β1-adrenergic inhibitor atenolol. Alveolar liquid clearance was inhibited by the sodium-channel inhibitor 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 vitro incubated lung tissue. The results suggest that alveolar liquid clearance in guinea pigs is mediated partly through amiloride-sensitive sodium channels and that alveolar liquid clearance can be increased by stimulation of primarily β1-adrenergic receptors.