Effect of nutritional status on the lung surfactant system: food deprivation and caloric restriction.

It has been reported that food deprivation may result in decreased synthesis of lung surfactant phospholipids while the ratio of saturated and unsaturated fatty acids of phosphatidylcholine is maintained. To further investigate this effect, rats were deprived of diet for 24, 48, 72, or 96 hr or fed a nutritionally complete but calorie-deficient diet for 48, 96, 144, and 192 hr. The surfactant was separated into extracellular and intracellular fractions, with the remaining lung tissue pooled as a nonsurfactant fraction. The total phospholipids, phosphatidylcholine, phosphatidylglycerol, and disaturated phosphatidylcholine of each surfactant fraction and the remaining lung tissue were analyzed. The data suggest that on a DNA basis, food and caloric deprivation results temporarily in an altered quantity of pulmonary phospholipids. By 96 hr of fasting or 192 hr of calorie-deficient diet, the pool sizes were replenished and no longer significantly different from the control state. In addition, the distribution of phosphatidylglycerol and phosphatidylcholine was modified in extracellular and intracellular surfactant fractions and in the nonsurfactant tissue fraction. Although the percentage of total phospholipids found as phosphatidylcholine was decreased, the relationship between saturated and unsaturated phosphatidylcholine was preserved in the extracellular surfactant fraction. These results demonstrate that during food and caloric deprivation, the lung quickly adapts to maintain the quality and quantity of surfactant on the alveolar surface.