ARACHIDONIC-ACID, PROSTAGLANDIN-E2 AND LEUKOTRIENE C-4 LEVELS IN GINGIVA AND SUBMANDIBULAR SALIVARY-GLANDS OF RATS FED DIETS CONTAINING N-3 FATTY-ACIDS

The effect of dietary n-3 fatty acids on prostaglandin E2 (PGE2) and leukotriene C4 (LTC4) levels in rat salivary glands and gingiva was examined in two separate nutritional studies. In the first set of experiments, two groups of male weanling Sprague-Dawley rats were fed semipurified diets containing 10% corn oil (control group) or 10% menhaden oil (experimental group). Rats were killed after 8 wk on the diets; the fatty acid composition of total phospholipids and the concentrations of PGE2 and its precursor, arachidonic acid, were measured in gingiva and submandibular salivary glands (SMSG). Dietary n-3 fatty acids were incorporated into the tissue phospholipids. Arachidonic acid levels were reduced by 56% in gingiva and SMSG of rats fed menhaden oil compared with the control rats fed the diet containing corn oil. The concentrations of PGE2 in SMSG and gingiva of rats fed the diet containing menhaden oil were reduced by 74% and 83%, respectively. In a subsequent nutritional study, we tested whether the diet-induced reduction in tissue arachidonic acid levels would also result in a corresponding decrease in LTC4 production. Three groups of rats were fed diets containing 5% corn oil (group 1), 4% ethyl ester concentrate of n-3 fatty acids plus 1% corn oil (group 2), or 5% ethyl ester concentrate of n-3 fatty acids (group 3). After 6 wk of feeding, gingiva and SMSG were analyzed for arachidonic acid content and in vitro production of LTC4. Arachidonic acid content of total phospholipids was about 60% lower in gingiva and 69% lower in SMSG of rats fed the ethyl ester concentrate of n-3 fatty acids (groups 2 and 3) than those of the control group fed the corn oil diet (group 1). Upon incubation with calcium ionophore, gingiva and SMSG from rats fed the n-3 fatty acids rich diet produced significantly less LTC4 than those from rats of the control group. Because PGE2 and LTC4 are believed to be important biochemical mediators of periodontal disease, one may speculate that a diet-induced reduction in their levels may have a beneficial effect upon the course of the disease. The function of salivary glands may also be altered because of the role of these eicosanoids in salivary secretions.