2000 Fiscal Year Final Research Report Summary
The role of androgen for the production of pulsatile secretion of growth hormone.
| Project/Area Number |
11671100
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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 |
Endocrinology
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| Research Institution | Institute of Gerontology, Nippon Medical School |
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Principal Investigator |
MINAMI Shiro Nippon Medical School Institute of Gerontology Professor, 老人病研究所, 教授 (10192361)
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| Project Period (FY) |
1999 – 2000
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| Keywords | growth hormone / ultradian rhythm / androgen / somatostatin / hypothalamus / c-fos |
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| Research Abstract |
There is a striking sex difference in the pattern of growth hormone (GH) secretion in rats. It has been shown that 2 weeks treatment with dihydrotestosterone (DHT) produces male-like secretory pattern of GH in ovariectomized (OVX) female rats. To elucidate the mechanism by which androgen masculinize GH secretory pattern, we have examined the acute effects of androgen on changes of the secretory pattern of GH, and then, the primary site of action of androgen.
(1) The subcutaneous administration of 0.01-1.0 mg of DHT produced male-like pattern of GH secretion in OVX rats within 6-12 h, but not in normal female rats. (2) DHT did not produce any changes of GH secretion in OVX rats with the anterolateral deafferentation of the medial basal hypothalamus which disrupted the interaction between the anterolateral area of the hypothalamus and the medial basal hypothalamus. (3) DHT, 1 μg, was microinjected directly into the restricted areas of the brain of the OVX rats to determine the primary site of action of DHT to masculinize GH secretion. DHT injection into the medial preoptic nucleus (MPO) or its vicinity effectively changed the GH secretion to male pattern, whereas the injection into the other areas was not effective. (4) The intravenous administration of DHT induced c-fos mRNA in most of the areas known to be positive for androgen receptor, including the MPO.
It is concluded that the MPO is the site where androgen acts to produce male-like secretory pattern of GH, and that estrogen in intact female rats prevents the masculinizing effect of androgen.
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