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| Daily rhythms of CRH, urotensinⅠand Ⅱgene expression and hormone secretion in the caudal neurosecretory system of Japanese Flounder (Paralichthys olivaceus) |
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| Abstract: |
| The caudal neurosecretory system (CNSS) is a unique neuroendocrine structure for environmental adaptation in fish, and is the major site of expression and secretion of corticotropin-releasing hormone (CRH), urotensin I (UⅠ) and II (UⅡ). This study examined daily changes of mRNA expression and the secretion profile in the CNSS of adult Japanese Flounder. Real Time-PCR result showed that under diurnal cycle, the expression of CNSS UⅠand UⅡmRNA was no significant difference; however, the expression of CRH mRNA was significantly higher at 12:00 than that at 6:00, after 12:00 CRH mRNA had a decreasing tendency. The calculated acrophase of CRH, UⅠand UⅡmRNA in the CNSS were recorded at 12:00, 18:00, 12:00, respectively. Moreover, immunocytochemistry revealed that total numbers of CRH, UⅠand UⅡimmunoreactive cells did not show significant daily differences. Plasma hormone was determined in triplicate by enzyme-linked immuneosorbent assay(ELISA) and radioimmunoassay(RIA). There was no statistical difference about plasma CRH, UⅠ， UⅡ, cortisol and adrenocorticotrophic hormone (ACTH) between daytime and nighttime, however, plasma UⅠa， UⅡand ACTH level went up at the beginning and then dropped till the end. These results suggest that the hormone secretion and gene expression in caudal neurosecretory system of Japanese Flounder has daily rhythm. These results reveal the importance of CNSS in the process of Japanese flounder’s adaption to environmental changes. |
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