Ventilatory and Cholinergic Control of Pulmonary Surfactant in the Rabbit

Four sets of experiments on surfactant secretion were performed using New Zealand rabbits under light pentobarbital anesthesia. Pa02, Paco2, and pHa remained normal during all experiments. In controls lung lavage yielded 1.62 +/- 0.26 (SD) mg of alveolar phospholipid (PL)/g lung; disaturated phosphatidylcholine comprised 55.5% of total PL. a) Acetylcholine infusion into the left pulmonary artery for 1-4 h caused a 13% increase in alveolar PL of left as compared to right lung. b) Efferent left vagus stimulation for 1 h increased alveolar PL of right and left lungs 31% as compared to controls (P = 0.012). c) Increasing minute ventilation by 100% by augmenting dead space for periods of 1, 2, and 4 h, increased alveolar PL 45% (P = 0.001), 54%, (P = 0.002), and 25% (P = 0.004), respectively, compared to controls. d) Administration of atropine prevented the increase in alveolar PL caused by increased ventilation. These findings show that increased ventilation can stimulate surfactant release through a cholinergically mediated mechanism but do not rule out the participation of other mechanisms.