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Identification of binding sites for an insulin-like growth factor (IGF-I) in the median eminence of the rat brain by quantitative autoradiography.
Endocrinology ; 119(2): 943-5, 1986 Aug.
Article in En | MEDLINE | ID: mdl-3015561
ABSTRACT
The microanatomical location of IGF-I binding in the rat brain was determined by in vitro autoradiography with slide-mounted sections of frozen brain. Sections incubated in 0.1 nM [125I]-iodo-IGF-I produced a dense grain concentration in regions of the autoradiographic image corresponding to the external palisade zone of the median eminence; other hypothalamic regions were not so heavily labeled. This reaction was significantly reduced in the presence of 100 nM IGF-I. Measurement of binding by computer digital image analysis of autoradiographic images showed that specific binding for IGF-I in the median eminence was 41.3 +/- 8 X 10(-3) fmol/mm2 (mean +/- SEM); nonspecific binding was 11.9 +/- 1.8 X 10(-3) fmol/mm2. In contrast, specific binding to other hypothalamic regions was uniformly lower. In a separate experiment, 1000 nM unlabeled insulin was added. Without insulin, specific binding was 23 +/- 0.9 X 10(-3) fmol/mm2; nonspecific binding was 8 +/- 0.5 X 10(-3) fmol/mm2. In the presence of 1000 nM unlabeled insulin, specific binding for [125I]-iodo-IGF-I was 23 +/- 1 X 10(-3) fmol/mm2. The results suggest that a high concentration of receptors for an IGF-I-like molecule is present in the median eminence.
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Database: MEDLINE Main subject: Somatomedins / Insulin-Like Growth Factor I / Receptors, Cell Surface / Median Eminence Type of study: Diagnostic_studies / Prognostic_studies Limits: Animals Language: En Year: 1986 Type: Article
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Database: MEDLINE Main subject: Somatomedins / Insulin-Like Growth Factor I / Receptors, Cell Surface / Median Eminence Type of study: Diagnostic_studies / Prognostic_studies Limits: Animals Language: En Year: 1986 Type: Article