2000 Fiscal Year Final Research Report Summary
Regulation of fish phagocytic functions by hormones and neurotransmitters
| Project/Area Number |
10460089
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | Miyazaki University |
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Principal Investigator |
IIDA Takaji Miyazaki University, Faculty of Agriculture, Professor, 農学部, 教授 (70159557)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAI Masahiro Miyazaki University, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (20178536)
ENDO Makoto Miyazaki University, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (80128355)
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| Project Period (FY) |
1998 – 2000
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| Keywords | stress / hormone / neurotransmitter / neutrophil / eosinophilic granular cell / head kidney phagocyte / respiratory burst / phagocytosis |
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| Research Abstract |
Plasma cortisol level of subordinate tilapia under social stress increased significantly, and neutrophil defense activities (respiratory burst and phagocytosis) from the subordinate fish were suppressed. Neutrophils incubated in a medium containing cortisol were impaired in their defense activities. From these results, cortisol could affect the neutrophil activities directly. Tissue-resident eosinophilic granular cells (EGCs), in which neutrophil-migrating factor (s) could be included, were also adversely affected in their degranulation by cortisol. Impaired EGC degranulating activity by cortisol could be involved in less migration of neutrophils to the inflammatory site under stressful conditions. These impaired non-specific defense mechanisms could increase susceptibility to infections and allow the infections to spread in the stressed fish. In fact, cortisol-implanted tilapia had higher susceptibility to Edwardosiella tarda infection.
In contrast to cortisol, another stress hormone, β endorphin enhanced defense activities of head kidney phagocytes from rainbow trout in vivo and in vivo. Carp head kidney leucocytes also were stimulated by β endorphin in vitro. It is indicated that there are two types of stress hormones, phagocyte-inhibiting hormone and phagocyte-stimulating hormone.
A neurotransmitter, adrenarin reduced the neutrophil defense activities in vitro. Adrenarin β receptor could be associated with this inhibition, with propranolol, antagonist of adrenarin β receptor, blocking the adverse effect of adrenarin on neutrophils. Serotonin, another neurotransmitter, also suppressed respirator burst of tilapia neutrophils in vitro. From these results, it is suggested that fish defense system is closely related with the nervous system.
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