BIOCHEMISTRY OF SALIVARY LIPIDS

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The studies conducted during the previous years of this project provided detailed characterization of lipids in salivary gland secretions and concretions. The long-term objectives of the proposed investigations are: to define the relationship of salivary lipids to the protein and glycoprotein components of saliva in health and disease; and to establish the role of salivary lipids in the process of pellicle formation. The specific goals are: to determine the content and composition of lipids associated with the low and high molecular weight mucin-type glycoproteins purified from submandibular-sublingual saliva; to establish the structural requirements of glyceroglucolipids for interacting with the low and high molecular weight mucins, and to determine whether this interaction involves the protein or carbohydrate component of mucins; to determine the effect of lipids on the rheological properties of salivary mucins; to isolate and characterize the lipoproteins from parotid saliva; to study the biosynthesis of glyceroglucolipids in salivary glands; to characterize the lipids deposited on the tooth surfaces in the process of pellicle formation and to establish the requirements of glyceroglucolipids, in terms of other salivary lipids and/or proteins, for their adsorption on enamel surfaces; to advance our knowledge on the composition and levels of lipids in the secretions of the major and minor salivary glands in health and disease. The low and high molecular weight mucus glycoproteins will be isolated from submandibular-sublingual saliva of caries-resistant and caries-susceptible individuals by a two stage procedure of gel filtration followed by equilibrium centrifugation in CsCl density gradient. Separation of parotid saliva from caries-resistant and caries-susceptible subjects by flotation through NaBr density gradient will be employed for isolation of lipoproteins. Rat parotid and submandibular glands will be utilized in the in vitro studies on biosynthesis of glyceroglucolipids. The lipid components of the pellicle formed in vivo and in vitro will be analyzed. The in vitro pellicle formation system will be used to study the requirements of glyceroglucolipids for their adsorption on enamel surfaces. The data on lipids in the secretion of the major and minor salivary glands of patients with systemic and salivary gland diseases will be compared with those of healthy individuals.