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This Article Full Text Full Text (PDF) All Versions of this Article: JOE-08-0002v1 198/2/317    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Miquet, J. G Articles by Sotelo, A. I PubMed PubMed Citation Articles by Miquet, J. G Articles by Sotelo, A. I

Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Facultad de Farmacia y Bioquímica, Junín 956, C1113AAD Buenos Aires, Argentina¹ Geriatrics Research, Departments of Internal Medicine and Physiology, School of Medicine, Southern Illinois University, Springfield, Illinois 62794, USA

(Correspondence should be addressed to A I Sotelo; Email: aisotelo{at}qb.ffyb.uba.ar)

Chronically elevated levels of GH in GH-transgenic mice result in accelerated growth and increased adult body weight. We have previously described that the GH-induced JAK2/STAT5-signaling pathway is desensitized in the liver of transgenic mice overexpressing GH. However, these animals present increased circulating IGF-I levels, increased hepatic GHR expression, and liver organomegaly due to hypertrophy and hyperplasia, which frequently progress to hepatomas as the animals age, indicating that action of GH on the liver is not prevented. In the present study, we have evaluated other GH-signaling pathways that could be activated in the liver of GH-transgenic mice. Upon GH administration, normal mice showed an important increment in STAT3 phosphorylation level, but transgenic mice did not respond to acute GH stimulation. However, STAT3 was constitutively phosphorylated in transgenic mice, whereas its protein content was not increased. GH-transgenic mice showed overexpression of c-Src, accompanied by an elevation of its activity. Other signaling mediators including focal adhesion kinase, epidermal growth factor receptor, Erk, Akt, and mammalian target of rapamycin displayed elevated protein and basal phosphorylation levels in these animals. Thus, GH-overexpressing transgenic mice exhibit hepatic upregulation of signaling mediators related to cell proliferation, survival, and migration. The upregulation of these proteins may represent GH-signaling pathways that are constitutively activated in the presence of dramatically elevated GH levels throughout life. These molecular alterations could be implicated in the pathological alterations observed in the liver of GH-transgenic mice.