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      Perinatal Activity of the Hypothalamic-Pituitary-Gonadal Axis in the Lamb

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          Previous studies in this laboratory have shown the existence of an early postnatal activation of the hypothalamic-pituitary-gonadal axis (HPGA) in the male lamb which was present at 2 and 4 weeks of age. In order to define more precisely the time sequence of HPGA activity, we have studied the in vivo and in vitro testicular responsiveness to human chorionic gonadotropin (hCG) of the immature lamb at 1, 3, 7, 14, 21 and 28 days of life. Plasma testosterone (T) increments (Δ) after hCG were lower in 1-day-old animals than in other age groups. Testicular concentrations of T, dehydroepiandrosterone and 17-hydroxyprogesterone increased from 1 to 14 days. Testicular 17, 20 lyase activity rose significantly with age but was not influenced by hCG. hCG and dibutyryl cyclic AMP increased significantly the T production by enriched interstitial cell preparation at 1 3, and 7 days, the greatest response being found at 7 days. hCG also increased significantly the T production at 14 days. These data suggest that the lamb testis has the capacity to respond to hCG in vivo and to various stimuli in vitro from the 1st day of life and that the response reaches a plateau from 2 to 4 weeks after birth.

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          Author and article information

          Horm Res Paediatr
          Hormone Research in Paediatrics
          S. Karger AG
          25 November 2008
          : 15
          : 3
          : 179-188
          aEndocrine Laboratory, Centre de Recherche Pédiatrique, Hôpital Sainte-Justine, Montréal, Québ., Canada; bInserm U 34 and clnserm U 162, Lyon, France
          179447 Horm Res 1981;15:179–188
          © 1981 S. Karger AG, Basel

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          Pages: 10
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