Phosphatidylglycerol-deficient lung surfactant has normal properties.

We have investigated the effects of substituting phosphatidylinositol (PI) for phosphatidylglycerol (PG) on the functional properties of rabbit lung surfactant. We gave oral 10% glucose solution for 3 days to 11 rabbits and 10% inositol to 12 others. Lung lavage surfactant phospholipids were normal in both groups, except that PG was low and PI was high in the inositol group. Fatty acyl group distributions did not differ, except for a slight decrease of oleic acid in the inositol group. Electron microscopic examination showed normal surfactant structure in both. The time course of surfactant adsorption to an air-water interface was similar in both groups. Minimum surface tension after film compression was 4.0 +/- 0.8 mN . m-1 in the glucose group and 2.9 +/- 1.3 mN . m-1 in the inositol group (mean +/- SE). Surface potential-surface pressure isotherms were identical to within 12 mV. Arterial blood gases breathing air and 100% O2 were the same in both groups, as were pressure-volume curves of excised lungs, with both air and saline filling. The results suggest that, if acidic phospholipids are necessary for maintaining normal surfactant structure and surface properties, normal pressure-volume relationships, and normal gas exchange, then PI may substitute for PG.