Divergent Effects of Estrogens on the Somatotropic Axis in Male and Female Calves
スポンサーリンク
概要
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This study describes 24 h profiles of growth hormone (GH) and of cortisol in male and female prepubertal calves before, during and after treatment with estradiol-17β (E<SUB>2</SUB>, silastic implants, 45 mg). Plasma concentrations of estradiol, testosterone and of insulin-like growth factor-1 (IGF-1) were also recorded. No significant (P<0.05) sex differences in GH, IGF-1 and in cortisol secretion were observed in untreated animals before E2-treatment. GH means, baselines and peak amplitudes increased during the treatment and remained elevated 1 week after removal of E<SUB>2</SUB> in female calves, but were unchanged in male calves. In contrast, IGF-1 plasma concentrations were increased in both sexes during and after E<SUB>2</SUB>-treatment. In males maximal IGF-1 concentrations were higher than in females. Cortisol profiles showed a high individual variability and no consistant changes related to sex or E<SUB>2</SUB>-stimulation. Based on the observation that the male calves already had a significant testosterone secretion, we conclude that the observed sex differences of GH-secretion in response to E<SUB>2</SUB> are related to endogenous testosterone. The E<SUB>2</SUB>-stimulated increase of IGF-1 plasma concentrations in males appears as related to an altered GH responsiveness rather than to changes in GH secretory patterns.
著者
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Meyer H
Techinische Univ. Muenchen Ferising Deu
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Schams Dieter
Institut Fur Physiologie Forschungszentrum Fur Milch Und Lebensmittel Weihenstephan Technische Unive
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SAUERWEIN Helga
Institut für Physiologie, Süddeutsche Versuchs- und Forschungsanstalt für Milchwirtschaft, Technisch
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MEYER Heinrich
Institut für Physiologie, Süddeutsche Versuchs- und Forschungsanstalt für Milchwirtschaft, Technisch
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Sauerwein H
Techinische Univ. Muenchen Ferising Deu
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MEYER Heinrich
Institut für Physiologie, Süddeutsche Versuchs- und Forschungsanstalt für Milchwirtschaft, Technische Universität München
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SAUERWEIN Helga
Institut für Physiologie, Süddeutsche Versuchs- und Forschungsanstalt für Milchwirtschaft, Technische Universität München
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