Phospholipid profiles in the salivary glands of rats of different ages

It has been reported that diabetes and Sjögren's syndrome patients exhibit variations in the amount of salivation and in the lipid components in saliva and salivary glands. We examined whether lipid compositions, especially phospholipid ones in the salivary glands of rats varied with aging. We analyzed phospholipid and fatty acid compositions in the salivary glands of young (5 to 6 weeks), adult (20 weeks), and old (50 weeks) rats and biochemical components in their blood. The aging (adult and old) rats had higher triacylglycerol, total lipid, total cholesterol and glucose contents in the plasma than the young one. The aging ones also had higher total lipid contents in the major salivary glands (parotid, submandibular and sublingual glands). They had higher wet weights of the major salivary glands and epididymal fat pads than the young ones, but had lower ratios of the major salivary glands to body weight. All of them had high phospholipid contents in the parotid and submandibular glands as compared to sublingual gland, but the aging ones had lower percentage of phospholipid contents of all salivary glands. Phosphatidylcholine and phosphatidylethanolamine were predominant among the phospholipids in the major salivary glands, and little difference was observed in phospholipid composition among the three groups. Palmitic and stearic acids (saturated acids), and linoleic, oleic and arachidonic acids (unsaturated acids) were major components of fatty acids of phospholipids in the major salivary glands. The aging ones had higher linoleic and lower arachidonic acid contents in the glands than the young one. In summary, the aging rats had higher total lipid contents than the young ones and had lower phospholipid contents of the major salivary glands. The n-6 fatty acid contents differed between aging and young ones. The results suggest that phospholipids in the major salivary glands change with the development of rat.