This project is concerned with the mechanism of coupling of macromolecule and electrolyte (fluid) secretion in the pancreas and parotid, using the rat as model. Our recent investigations of the electrolyte permeability properties of the membrane of isolated zymogen granules have demonstrated the presence of chloride (anion) transport pathways, which are activated in situ by pretreatment with secretagogues. Since the granule membrane serves as precursor for the luminal plasma membrane, these findings suggest that chloride secretion occurs across the granule membrane after its fusion with the plasma membrane and that the resulting fluid secretion serves to flush out the digestive enzymes from the former intragranular space. This mechanism would automatically couple fluid and macromolecule secretion. This proposal is specifically concerned with quantitative measurements of the chloride permeability of granule membranes, an evaluation of intracellular_signals involved in activation of its chloride permeability, and the biochemical changes in the membrane associated with activation. These goals will be accomplished by measuring the electrical and transport properties of isolated granule membranes, by comparison of the biochemical composition of membranes from isolated resting and secretagogue-activated granules, and by investigations of the activation process in an isolated rat pancreatic acinar preparation. The results should provide answers about contributions of the zymogen granule membrane to electrolyte secretion and about the intracellular signals and enzymes involved in normal activation_of chloride conductance in the luminal plasma membrane. The biochemical studies may also provide molecular information on the chloride transporters involved and the chemistry of their activation. Information of these processes is important for understanding the cell physiology of exocrine secretion and its pathophysiology as expressed, for example, in Cystic Fibrosis (CF) in the form of viscous secretions and ductal blockage of the pancreas.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK039658-03
Application #
3239521
Study Section
Cellular Biology and Physiology Subcommittee 1 (CBY)
Project Start
1989-08-01
Project End
1994-07-31
Budget Start
1991-08-24
Budget End
1992-07-31
Support Year
3
Fiscal Year
1991
Total Cost
Indirect Cost
Name
Case Western Reserve University
Department
Type
Schools of Medicine
DUNS #
077758407
City
Cleveland
State
OH
Country
United States
Zip Code
44106
Bertrand, C A; Laboisse, C L; Hopfer, U (1999) Purinergic and cholinergic agonists induce exocytosis from the same granule pool in HT29-Cl.16E monolayers. Am J Physiol 276:C907-14
Bertrand, C A; Durand, D M; Saidel, G M et al. (1998) System for dynamic measurements of membrane capacitance in intact epithelial monolayers. Biophys J 75:2743-56
Guo, X; Merlin, D; Harvey, R D et al. (1997) Pharmacological evidence that calcium is not required for P2-receptor-stimulated Cl- secretion in HT29-Cl.16E. J Membr Biol 155:239-46
Guo, X W; Merlin, D; Laboisse, C et al. (1997) Purinergic agonists, but not cAMP, stimulate coupled granule fusion and Cl- conductance in HT29-Cl.16E. Am J Physiol 273:C804-9
Merlin, D; Guo, X; Martin, K et al. (1996) Recruitment of purinergically stimulated Cl- channels from granule membrane to plasma membrane. Am J Physiol 271:C612-9
Guo, X; Merlin, D; Harvey, R D et al. (1995) Stimulation of Cl- secretion by extracellular ATP does not depend on increased cytosolic Ca2+ in HT-29.cl16E. Am J Physiol 269:C1457-63
Merlin, D; Guo, X; Laboisse, C L et al. (1995) Ca2+ and cAMP activate different K+ conductances in the human intestinal goblet cell line HT29-Cl.16E. Am J Physiol 268:C1503-11
Jarry, A; Merlin, D; Hopfer, U et al. (1994) Cyclic AMP-induced mucin exocytosis is independent of Cl- movements in human colonic epithelial cells (HT29-Cl.16E). Biochem J 304 ( Pt 3):675-8
Merlin, D; Augeron, C; Tien, X Y et al. (1994) ATP-stimulated electrolyte and mucin secretion in the human intestinal goblet cell line HT29-Cl.16E. J Membr Biol 137:137-49
Jarry, A; Merlin, D; Velcich, A et al. (1994) Interferon-gamma modulates cAMP-induced mucin exocytosis without affecting mucin gene expression in a human colonic goblet cell line. Eur J Pharmacol 267:95-103

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