A dual effector theory of growth-hormone action

Authors

  • Howard Green,

    1. Department of Physiology and Biophysics, Harvard Medical School, Boston, MA 021 15, USA
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  • Minom Morikawa,

    1. Department of Physiology and Biophysics, Harvard Medical School, Boston, MA 021 15, USA
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    • Institute for Production and Research Development, The Nikka Whisky Distilling Co. Ltd. 967 Matsuyama, Masuo Kashiwa, Chiba 277, Japan

  • Tracy Mxon

    1. Department of Physiology and Biophysics, Harvard Medical School, Boston, MA 021 15, USA
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    • ★★

      Massachusetts General Hospital, Department of Molecular Biology, Boston, MA 02114, USA


Abstract

Abstract. Growth hormone increases tissue formation by acting both directly and indirectly on target cells. The direct action promotes the differentiation of precursor cells; this has been demonstrated for two mesenchymal cell types. Insulin-like growth factor I (IGF-I) is not able to substitute for growth hormone in promoting this differentiation, but it is proposed that its mitogenic action selectively promotes cell multiplication in young differentiated clones. As tissue growth results from both the creation of new differentiated cells and their subsequent clonal expansion, both effectors increase tissue growth, but by different means.

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