DIBUTYRYL CYCLIC-GMP AND HYPERVENTILATION PROMOTE RAT LUNG PHOSPHOLIPID RELEASE

Ventilation of rats at high inspiratory pressures raises lung tissue content of guanosine 3',5'-cyclic monophosphate (cGMP). Hyperventilation in rabbits augments release of phospholipid into lavage fluid. Can cGMP, in the absence of hyperventilation, increase lung phospholipid release? Sprague-Dawley rats are injected with [14C]palmitate, and after 1.5 h are anesthetized and ventilated for 20 min. Three groups are ventilated at peak inspiratory pressures (PIP) of 10 cmH2O, while saline, dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP), or dibutyryl cGMP (DBcGMP) is infused into the pulmonary artery. In a fourth group, saline is infused into the pulmonary artery, but ventilation is performed with PIP of 25 cmH2O. Lung tissue and lavage fluid are then analyzed for phospholipid (PL) content and for incorporation of [14C]palmitate into lavage and tissue PL fractions. Ventilation at increased pressure and infusion of DBcGMP are associated with increases in release of labeled PL into lavage fraction. The findings suggest that the increase in lavage PL release associated with hyperventilation is, at least in part, mediated by cGMP.