The mechanism of secretion in salivary glands and the pancreas requires Ca2+ and the cyclic nucleotides, but the precise roles of those second messengers and the regulation of their cytosolic concentrations are only partially understood. These studies will evaluate the hypothesis that control of second messenger concentration effected, in part, by the second messengers themselves. This hypothesis will be tested in comparative studies using acinar preparations of the rat submandibular gland and pancreas as model systems to (1) characterize the kinetic and regulatory properties of the enzymes that control second messenger concentration: high affinity CaATPase and active Ca2+ translocation, adenylate and guanylate cyclase activities and cAMP and cGMP phosphodiesterase activities; and (2) characterize the kinetic properties of the forms of those enzymes regulated by the Ca2+-calmodulin complex. A second goal of these studies is to determine the effects of second messengers on kinase activities in exocrine glands and to evaluate the hypothesis that secretion depends on second messenger-regulated protein phosphorylation. Polyacrylamide gel electrophoresis and autoradiography will be used to detect and characterize the phosphorylated substrates of kinases regulated by the second messengers in broken acinar cells. In other studies, functioning acinar preparations will be incubated with P32 to label intracellular ATP then exposed to cholinergic, Alpha and Beta adrenergic or peptidergic agents. Secretory responses (in terms of release of K+, of amylase or as sialic acid liberated from secreted glycoproteins) will be measured at various times thereafter and correlated with changes in protein phosphorylation. In parallel studies, acini will be exposed to secretagogues in the presence of agents which inhibit, augment and/or mimic the effects of the second messengers in order to correlate changes in second messenger-dependent phosphorylation with changes in secretory response. These studies will yield new information concerning the mechanism of stimulus-secretion coupling in well-defined model exocrine systems and will provide new insights regarding the comparative physiology of secretory systems involved in a variety of diseases. In addition these studies will be important in defining the factors that regulate normal salivary gland function and therefore are important for the maintenance of healthy soft and mineralized tissue in the oral cavity.

National Institute of Health (NIH)
National Institute of Dental & Craniofacial Research (NIDCR)
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Oral Biology and Medicine Study Section (OBM)
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University of Missouri-Columbia
Schools of Medicine
United States
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Hurley, T W; Ryan, M P; Moore, W C (1996) Regulation of changes in cytosolic Ca2+ and Na+ concentrations in rat submandibular gland acini exposed to carbachol and ATP. J Cell Physiol 168:229-38
Hurley, T W; Ryan, M P; Shoemaker, D D (1994) Mobilization of Ca2+ influx, but not of stored Ca2+, by extracellular ATP in rat submandibular gland acini. Arch Oral Biol 39:205-12
Hurley, T W; Shoemaker, D D; Ryan, M P (1993) Extracellular ATP prevents the release of stored Ca2+ by autonomic agonists in rat submandibular gland acini. Am J Physiol 265:C1472-8
Hurley, T W; Brinck, R W (1992) Differential regulation of agonist-stimulated Ca2+ influx in acini of rat pancreas and submandibular gland. Arch Oral Biol 37:763-9
Hurley, T W; Ryan, M P; Brinck, R W (1992) Changes of cytosolic Ca2+ interfere with measurements of cytosolic Mg2+ using mag-fura-2. Am J Physiol 263:C300-7
Hurley, T W; Brinck, R W (1990) Regulating transient and sustained changes of cytosolic Ca2+ in rat pancreatic acini. Am J Physiol 258:C54-61
Brinck, R W; Hurley, T W (1989) Regulation of cytosolic Ca2+ in resting and stimulated rat submandibular salivary gland acini. Arch Oral Biol 34:917-22
Hurley, T W (1988) Kinetics of high-affinity Ca2+ sequestration in permeabilized rat pancreatic acini. Am J Physiol 254:C621-7
Hurley, T W; Ryan, M P (1988) The control of cytosolic Ca2+ concentration: studies of high affinity Ca2+ transport in permeabilized acini of rat submandibular glands. Arch Oral Biol 33:793-800
Hurley, T W; Martinez, J R (1987) Differential effects of chronic reserpine exposure on Ca2+ sequestering mechanisms in rat submandibular gland vesicles. Cell Calcium 8:353-63