The nature of dietary lipids and their levels can modify the structure and function of salivary glands in several different ways. A likely mode of action would be by virtue of their effect in inducing physiochemical modifications of plasma membrane lipids. Since membrane lipids play an important role in determining the activities of several membrane associated enzymes such as (Na+ + K+)-ATPase and adenyl cyclase in a number of tissues, it is quite likely that the activities of these two enzymes will be affected in salivary glands as well. If so, this may have a profound influence on salivary gland function because of the physiological importance of (Na+ + K+)-ATPase in active transport of ions and that of adenyl cyclase in the secretion of salivary proteins. The objective of the proposed studies is to test the above hypothesis using several nutritional models such as essential fatty acid deficiency, feeding of saturated versus unsaturated fats, cholesterol supplementation and trans fatty acids. Male weanling rats will be fed purified diets containing different levels of linoleic acid, trans fatty acids, cholesterol and two types of fats. At various time intervals, rats will be killed, their submandibular salivary glands (SMSG) will be dissected out and plasma membranes will be prepared. The activities of ouabain sensitive (Na+ +K+)-ATPase (EC 3.6.1.3) and adenyl cyclase (EC 4.6.1.1) will be determined in plasma membrane preparations and in gland homogenates. Fluidity of membranes will be determined by fluorescence spectroscopy using fluorescent probes. Aliquots of SMSG homogenates and plasma membranes will be extracted for lipids and the major phospholipids will be isolated by thin layer chromatography. The fatty acid composition of total lipids and phospholipids will be determined by gas chromatographic methods using packed and open tubular glass capillary columns. All data will be statistically analyzed in order to seek any correlations between the lipid composition, membrane fluidity and the activities of the two enzymes. Samples of submadibular saliva will also be obtained from some rats by duct cannulation. Salvia will be analyzed for total proteins, amylase, Na+ and K+. The effect of lipid nutrition on salivary gland plasma membrane lipid composition, fluidity, enzyme activities and saliva composition will be assessed.
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