DETANONOate, a nitric oxide donor, decreases amiloride-sensitive alveolar fluid clearance in rabbits

Inhaled nitric oxide (NO) has been administered to animals to selectively reduce pulmonary hypertension via NO donors such as the NONOates. However, vectorial Na⁺ transport across confluent monolayers of alveolar type II (ATII) pneumocytes has been decreased by NO. We tested the hypothesis that administration of the NO donor, DETANONOate, would decrease alveolar fluid clearance (AFC) in the rabbit in vivo. We instilled a solution of 5% albumin in 0.9% NaCl with 3 mM DETANONOate into anesthetized rabbits. Two hours later, similar AFC values were measured in the presence and absence of 3 mM DETANONOate (38 ± 12% versus 43 ± 13%; mean ± SD). However, animals coadministered 1 mM amiloride with one of three doses of DETANONOate (100 μM, 300 μM, or 3 mM) had significantly (p < 0.05) greater AFC values (23 ± 8, 20 ± 14, 28 ± 12%, respectively) than those administered amiloride alone (10 ± 7%). When 5% albumin in a Cl^--free solution was administered in the presence or absence of 100 μM DETANONOate, neither AFC values nor alveolar Cl^- concentrations were different. DETANONOate decreases the amiloride- sensitive fraction of AFC but does not decrease total AFC. DETANONOate does not influence total AFC secondary to an increase in the amiloride-insensitive fraction of AFC that is not associated with a decrease in alveolar Cl^- secretion.