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      Lack of Evidence for Acute Effects of Growth Hormone-Releasing Hormone on Serum Insulin and Glucose Levels in Normal and Hypophysectomized Rats

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          Abstract

          Growth hormone (GH) is diabetogenic but has also been suggested to stimulate insulin release. Our aim was to study whether acute effects of GH on serum insulin and glucose concentrations can be observed when GH release is physiologically induced by GH-releasing hormone (GHRH), which is known to stimulate insulin secretion. We also studied the acute effects of GHRH as such on insulin release in vivo and in vitro. Female Sprague-Dawley rats were hypophysectomized (hypox) at 40 days of age. At day 188, rats received 1 μg GHRH( 1-29)/100 g body weight i.v. In sham-operated rats, GHRH induced a rise in serum GH from 36.5 ± 1.9 ng/ml (time 0 min) to 560.0 ± 13.3 ng/ml (5 min;) (n = 6; p < 0.001). In hypox rats, no measurable serum levels of GH were detected either before or after GHRH treatment. Serum insulin was unaffected by GHRH in both groups of animals. Serum glucose was higher in sham operated than in hypox rats (7.3 ± 0.4 vs. 6.3 ± 0.1 mM at 0 min; p < 0.01). Serum glucose did not rise following GHRH injection. In isolated rat islets, cultured for 3 days at 11.1 m M glucose, 0.1-10 n M GHRH stimulated basal insulin release at 3 m M glucose. To summarize, GHRH at high concentrations stimulates insulin release in vitro, but neither GHRH, at a concentration where GH secretion is greatly stimulated, nor GHRH-induced GH release, have any acute effects on serum insulin or glucose levels.

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          Author and article information

          Journal
          HRE
          Horm Res Paediatr
          10.1159/issn.1663-2818
          Hormone Research in Paediatrics
          S. Karger AG
          1663-2818
          1663-2826
          1994
          1994
          05 December 2008
          : 41
          : 1
          : 21-26
          Affiliations
          Department of Histology and Cell Biology, University of Umeå, Sweden
          Article
          183872 Horm Res 1994;41:21–26
          10.1159/000183872
          8013938
          © 1994 S. Karger AG, Basel

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          Page count
          Pages: 6
          Categories
          Original Paper

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