COMPOSITION OF PHOSPHOLIPID CLASSES AND PHOSPHATIDYLCHOLINE MOLECULAR-SPECIES OF GASTRIC-MUCOSA AND MUCUS

Phospholipids have been proposed to protect the gastric mucosa by form ing a proton-repellant hydrophobic layer on the gastric luminal surfac e, acting as a so-called gastric surfactant. The composition of this h ydrophobic phospholipid layer has not previously been analysed in deta il. Therefore, we measured the composition of phospholipid classes and phosphatidylcholine (PC) molecular species in gastric mucosa and mucu s of rats and pigs using high resolution HPLC techniques. The predomin ant phospholipids of both mucosa and mucus were PC and phosphatidyleth anolamine (PE). Little phosphatidylglycerol was present. The most abun dant PC species of rat mucosa were PC16:0/18:1, PC16:0/18:2, PC16:0/20 :4 and PC18:0/20:4. Pig mucosa also contained PC16:0/18:1, PC16:0/18:2 , and PC18:0/20:4, but was poor in PC16:0/20:4. Dipalmitoyl-PC (PC16:0 /16:0), the surface-active component of pulmonary surfactant, comprise d only 6.42 +/- 0.33% of total PC in rat mucosa and only 5.50 +/- 1.46 % of total PC in pig mucosa. Gastric mucus, isolated from both rat and pig, contained largely PC16:0/18:1 and PC16:0/18:2. The content of PC 16:0/16:0 was even lower in mucus than ih mucosal PC (rat 2.86 +/- 0.4 0%, P < 0.01; pig 1.92 +/- 0.55%, P < 0.05). We conclude that, in cont rast to pulmonary surfactant, any surfactant function of the hydrophob ic barrier of the stomach is unlikely to be mediated by PC16:0/16:0.