Ventilatory and cholinergic control of pulmonary surfactant in the rabbit

Abstract

Four sets of experiments on surfactant secretion were performed using New Zealand rabbits under light pentobarbital anesthesia. PaO2 [arterial blood O2 tension], PaCO2 [arterial blood CO2 tension] and pHa [arterial pH] 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. 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. Efferent left vagus stimulation for 1 h increased alveolar PL of right and left lungs 31% as compared to controls (P = 0.012). 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. Administration of atropine prevented the increase in alveolar PL caused by increased ventilation. Increased ventilation can stimulate surfactant release through a cholinergically mediated mechanism but other mechanisms may also be involved.