2000 Fiscal Year Final Research Report Summary
Mechanisms by which protein kinases modify catecholamine secretion and analyses of them by evanescent-wave fluorescence microscopy
| Project/Area Number |
10670037
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General physiology
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| Research Institution | NIIGATA UNIVERSITY |
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Principal Investigator |
WARASHINA Akira School of Medicine, NIIGATA UNIVERSITY, Associate Professor, 医学部, 助教授 (50064580)
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| Project Period (FY) |
1998 – 2000
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| Keywords | chromaffin cell / catecholamine secretion / protein kinase C / nicotine / muscarine / evanescent-wave microscope / acridine orange / exocytosis |
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| Research Abstract |
Effects of the activation of different types of protein kinases in adrenal chromaffin cells on secretory responses stimulated by various secretagogues were analyzed. The following results were obtained.
1. Ca^<2+>-indicator-loaded chromaffin cells in the perfused rat adrenal medulla were stimulated by various stimulants and changes in [Ca^<2+>]_i (Ca-response) and in catecholamine secretion (secretory response) were measured simultaneously. On activating protein kinase C (PKC) with phorbol dibutyrate, secretory processes were affected through at least, two different pathways. One is to inhibit the early-stage of secretory processes stimulated by muscarine, bradykinin and histamine. This inhibition was associated with a reduction of Ca^<2+> entry mediated by the receptor/G-protein. The other is to promote the late-stage of secretory processes occurring after an increase in [Ca^<2+>]_i. This promotion involves any kind of secretagogues including nicotine and the receptor agonists mentione
… More
d above. The activation of PKA with forskolin promoted the late-stage of secretory processes in a similar manner to PKC.Although wortmannin and LY29004 have been reported to suppress catecholamine secretion by inhibition of Pl3-kinase, these agents may reduce Ca^<2+> entry through their nonspecific effects on Ca^<2+> channels.
2. To investigate the mechanism by which PKC promote the late-stage secretory processes, the evanescent-wave fluorescence microscopy was applied to visualize secretory granules near plasma membrane of chromaffin cells. Some of acridine orange-stained granules were disappeared when cells were stimulated by electrical stimuli, indicating that observed granules were docked on the membrane to prepare exocytotic secretion. It was found in a cooperative study with Dr.Terakawa at Hamamatsu Medical School that the activation of PKC increases the number of granules docking on the plasma membrane. This result may provide one of possible mechanisms by which PKC promotes the late-stage of secretory processes. Less
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