title: GH administration patterns differently regulate epidermal growth factor signaling.
abstract: Current GH administration protocols imply frequent s.c. injections, resulting in suboptimal compliance. Therefore, there is interest in developing delivery systems for sustained release of the hormone. However, GH has different actions depending on its continuous or pulsatile plasma concentration pattern. GH levels and circulating concentration patterns could be involved in the regulation of epidermal growth factor receptor (EGFR) expression in liver. Aberrant expression of this receptor and/or its hyperactivation has been associated with the pathogenesis of different types of carcinoma. Considering that one of the adverse effects associated with GH overexpression and chronic use of GH is the increased incidence of malignancies, the aim of this study was to analyze the effects of GH plasma concentration patterns on EGFR expression and signaling in livers of mice. For this purpose, GH was administered by s.c. daily injections to produce an intermittent plasma pattern or by osmotic pumps to provoke a continuously elevated GH concentration. Intermittent injections of GH induced upregulation of liver EGFR content, augmented the response to EGF, and the induction of proteins involved in promotion of cell proliferation in female mice. In contrast, continuous GH delivery in male mice was associated with diminished EGFR in liver and decreased EGF-induced signaling and expression of early genes. The results indicate that sustained delivery systems that allow continuous GH plasma patterns would be beneficial in terms of treatment safety with regard to the actions of GH on EGFR signaling and its promitogenic activity.
authors.affiliation: Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Universidad de Buenos Aires, Junín 956, 1113 Ciudad de Buenos Aires, Argentina Instituto de Biología y Medicina Experimental, CONICET, Vuelta de Obligado 2490, 1428 Ciudad de Buenos Aires, Argentina.
authors.forename: María E
authors.initials: ME
authors.lastname: Díaz
authors.forename: Johanna G
authors.initials: JG
authors.lastname: Miquet
authors.forename: Soledad P
authors.initials: SP
authors.lastname: Rossi
authors.forename: Pablo E
authors.initials: PE
authors.lastname: Irene
authors.forename: Ana I
authors.initials: AI
authors.lastname: Sotelo
authors.forename: Mónica B
authors.initials: MB
authors.lastname: Frungieri
authors.forename: Daniel
authors.initials: D
authors.lastname: Turyn
authors.forename: Lorena
authors.initials: L
authors.lastname: González
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D004334:Drug Administration Schedule; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D013006:Growth Hormone / Q000008:administration & dosage* / Q000097:blood; D007260:Infusion Pumps; D007267:Injections; D008297:Male; D051379:Mice; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: D004815:Epidermal Growth Factor; D013006:Growth Hormone; C541485:EGFR protein, mouse; D066246:ErbB Receptors
keywords: epidermal growth factor; growth hormone; intracellular signaling; liver