Control of lung surfactant by ventilation, adrenergic mediators, and prostaglandins in the rabbit

In a previous study, we showed that increasing minute ventilation (VE) in rabbit lung by adding a dead space augmented pulmonary surfactant in the airspaces by a cholinergically mediated mechanism. Using the same model in the present study of 148 rabbits, we found that increasing VE augmented airspace phospholipid, the main component of surfactant, from 2.50 +/- 0.61 (mean +/- SD) mg per g of lung during normal VE to 3.15 +/- 1.22 (mean +/- SD) mg per g of lung during increased VE (P = 0.02). Both blocking beta-adrenergic receptors with propranolol or sotalol and inhibiting prostaglandin synthetase with indomethacin or sodium meclofenamate prevented the expected increase in phospholipid during increased VE (P is less than 0.05). The beta-2 agonist, terbutaline, increased phospholipid by 43 per cent during normal VE (P is less than 0.01), and propranolol blocked this increase (P is less than 0.05). Isoproterenol, arachidonic acid, prostaglandins E1, E2, F2alpha, and a cyclic endoperoxide analog of prostaglandin H2 (U-46619) injected during normal VE failed to increase phospholipid. We concluded that acetylcholine (previous study), beta-adrenergic mediators, and prostaglandins are involved in controlling alveolar surfactant during increased VE.