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      Plasma and Pituitary Concentration of Growth Hormone in Male and Female Rats during a 24-Hour Period


      Hormone Research in Paediatrics

      S. Karger AG

      Plasma GH, Pituitary GH, Circadian rhythm

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          The aim of this study was to investigate the pattern of growth hormone (GH) secretion during a 24-hour period in the rat, in order to determine whether differences in plasma GH between male and female animals could be demonstrated. The daily fluctuations of plasma GH were characterized by three major bursts of secretion occurring at 09.00, 16.30 and 21.00 h in both sexes. In females, the three peaks were of the same extent, while in males the night peak was greater than the other two. Female rats maintained higher GH levels than males at 09.00, 12.00 and 16.30 h, while no differences between both sexes were found at all other times. These results show that sampling time seems to be of great importance in evaluating the differences in plasma GH concentration between experimental groups in which there could be marked differences in the daily patterns of hormone secretion.

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          Author and article information

          Horm Res Paediatr
          Hormone Research in Paediatrics
          S. Karger AG
          25 November 2008
          : 14
          : 2
          : 130-137
          Departamento de Endocrinología Experimental, Instituto ‘G. Marañon’, y Facultad de Medicina de la Universidad Autónoma de Madrid, Madrid, España
          179369 Horm Res 1981;14:130–137
          © 1981 S. Karger AG, Basel

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          Pages: 8
          Original Paper


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