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  • 1
    Electronic Resource
    Electronic Resource
    Effects of trypsin on secretion stimulated by micromolar Ca2+ and phorbol ester in digitonin-permeabilized adrenal chromaffin cells (1988)
    Springer
    Cellular and molecular neurobiology 8 (1988), S. 115-128 
    Details
    ISSN: 1573-6830
    Keywords: adrenal gland ; chromaffin cells ; phorbol ester ; digitonin ; secretion ; calcium ; trypsin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Catecholamine secretion from digitonin-treated chromaffin cells is stimulated directly by micromolar Ca2+ in the medium. The permeabilized cells are leaky to proteins. 2. In this study trypsin (30–50µg/ml) added to cells after digitonin treatment completely inhibited subsequent Ca2+-dependent catecholamine secretion. The same concentrations of trypsin did not inhibit secretion from permeabilized cells if trypsin was present only prior to cell permeabilization. 3. The data indicate that trypsin entered digitonin-treated chromaffin cells which were capable of undergoing secretion and that an intracellular, trypsinsensitive protein is involved in secretion. Chymotrypsin was less potent but had effects similar to those of trypsin. 4. The enhancement of Ca2+-dependent secretion from permeabilized chromaffin cells induced by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) was inhibited by trypsin added simultaneously with Ca2+ to permeabilized cells at concentrations (3–10µg/ml) which had little or no effect on Ca2+-dependent secretion from cells untreated with TPA. Ca2+-dependent secretion in TPA-treated cells was reduced by trypsin only to the level that would have occurred in cells not treated with TPA. Trypsin reduced the large TPA-induced increment of membrane-bound protein kinase C. 5. The data indicate that Ca2+-dependent secretion in the absence of TPA does not require aTPA-like effect of Ca2+ to activate protein kinase C. Protein kinase C activation by TPA probably enhances Ca2+-dependent secretion by modulating the normal Ca2+-dependent pathway or by activating another Ca2+-dependent pathway which functions in parallel to the normal pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00712917
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Calcium promotes the accumulation of polyphosphoinositides in intact and permeabilized bovine adrenal chromaffin cells (1991)
    Springer
    Cellular and molecular neurobiology 11 (1991), S. 357-370 
    Details
    ISSN: 1573-6830
    Keywords: polyphosphoinositides ; calcium ; chromaffin cells ; lipid metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Because cellular pools of phosphatidylinositol phosphate and phosphatidylinositol bisphosphate turn over rapidly during phospholipase C stimulation, the continuing production of inositol phosphates requires continuing synthesis from phosphatidylinositol of the polyphosphoinositides. In the present study in adrenal chromaffin cells, we examined the effects of nicotinic stimulation and depolarization in intact cells and micromolar Ca2+ in permeabilized cells on the levels of labeled polyphosphoinositides. We compared the effects to muscarinic stimulation in intact cells and GTPγS in permeabilized cells. 2. Nicotinic stimulation, elevated K+, and muscarinic stimulation cause similar production of inositol phosphates (D. A. Eberhard and R. W. Holz,J. Neurochem. 49:1634-1643, 1987). Nicotinic stimulation and elevated K+ but not muscarinic stimulation increased the levels of [3H]inositol-labeled phosphatidylinositol phosphate by 30–60% and [3H]phosphatidylinositol bisphosphate by 25–30%. The increase required Ca2+ in the medium, was maximal by 1–2 min, and was not preceded by an initial decrease in phosphatidylinositol phosphate and phosphatidylinositol bisphosphate. 3. In digitonin-permeabilized cells, Ca2+ caused as much as a twofold increase in [3H]phosphatidylinositol phosphate and [3H]phosphatidylinositol bisphosphate. Similarly, Ca2+ enhanced the production of [32P]phosphatidylinositol phosphate and [32P]phosphatidylinositol bisphosphate in the presence of [γ-32P]ATP. In contrast, GTPγS in permeabilized cells decreased polyphosphoinositides in the presence or absence of Ca2+. 4. The ability of Ca2+ to increase the levels of the polyphosphoinositides decayed with time after permeabilization. The effect of Ca2+ was increased when phosphoesterase and phospholipase C activities were inhibited by neomycin. 5. These observations suggest that Ca2+ specifically enhances polyphosphoinositide synthesis at the same time that it activates phospholipase C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00713279
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    Paper (German National Licenses)
    Fulltext
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