Localization and physiological functions of SRIF receptor and GHRH receptor in the rat pituitary
| Project/Area Number |
08680872
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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 |
Neuroscience in general
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| Research Institution | Nippon Medical School |
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Principal Investigator |
KATO Masakatsu Nippon Medical School, Department of Physiology I,Assistant Professor, 医学部, 講師 (90143239)
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| Co-Investigator(Kenkyū-buntansha) |
SAKUMA Yasuo Nippon Medical School, Department of Physiology I,Professor, 医学部, 教授 (70094307)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1997: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1996: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | pituitary / somatotroph / folliculo-stellate cell / GHRH / somatostatin / 成長ホルモン放出ホルモン(GHRH) / ソエトスタチン(SRIF) / GHRH受容体 / SRIF受容体 / ソマトスタチン(SRIF) |
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| Research Abstract |
In the present research, we analyzed the effects of somatostatin (SRIF) and growth hormone releasing hormone (GHRH) on male rat pituitary cells in primary culture. Among pituitary cells we focused somatotrophs and folliculo-stellate cells.
First, we analyzed the effects of these peptides on somatotrophs by a perforated patch clamp method and revealed following things. GHRH augmented the voltage-gated sodium current. In addition, GHRH elicited persistent sodium current at the potential more positive than-60mV.The former current was completely blocked by tetrodotoxin, whereas the latter current was not affected by that. On the other hand, SRIF had no effect on the voltage-gated sodium current, while that attenuated the GHRH-induced persistent sodium current. These results indicate (i) that GHRH augments basal GH secretion by facilitating the voltage-gated sodium current ; (ii) that GHRH-induced sodium current depolarizes somatotrophs which activates the voltage-gated calcium current, whereby facilitating GH secretion ; (iii) SRIF suppresses GH secretion not only by activating the inward rectifier potassium current but also attenuating the GHRH-induced sodium current.
Second, we analyzed the effects of these peptides on folliculo-stellate cells by the method of calcium-imaging, GHRH affects intracellular calcium concentration ([Ca^<2+>]i) in 30% of cells in the total examined. Among responding cells, 95% of them responded to GHRH by augmenting [Ca^<2+>]i and remaining cells by suppressing [Ca^<2+>]i. Both responses were blocked by removing calcium from extracellular solution. SRIF suppressed the GHRH-induced responses in 70% of the cells without affecting remaining 30% of the cells. These results indicate that a substantial proportion of folliculo-stellate cells possesses the receptors for GHRH and SRIF and that the peptides regulate their function.
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Report
(3 results)
Research Products
(21 results)
