SHORT COMMUNICATION Comparison of physical properties of membrane phospholipid liposomes in rat salivary glands

Many membrane bound proteins are closely associated with lipids. These membrane lipids are not only structural components of cellular compartmentation but also functionally important elements involved in some are of the biological functions of membrane proteins1). With respect to the dynamic structure of membranes, there is evidence that membrane fluidity may play an important role in some biological functions1,2). The hormoneor neurotransmitter-dependent and membrane bound receptor functions are also affected by membrane fluidity3,4). This fluidity is regulated mainly by phospholipids, their fatty acyl and polar head moieties, and cholesterol5-9). On the other hand, salivary glands are continuously controlled by the autonomic nervous system and quickly respond to various agonists resulting in saliva secretion10). Although there are three major glands, parotid, submandibular and sublingual, in rat salivary glands, the sublingual gland differs from the other two, because it is unresponsive to ƒÀ -adrenergic agonist , isoproterenol, and only minimally to epinephrine11). Furthermore, in our previous reports12,13), membrane phos-