title: Distinct neuronal growth hormone receptor ligand specificity in the rat brain.
abstract: A cerebral growth hormone axis is activated during recovery from brain injury and centrally administered growth hormone can rescue injured neurons. It remains unclear, however, whether this treatment effect occurs directly via neuronal growth hormone receptors. Immunohistochemistry confirmed growth hormone receptor protein on neuronal cell bodies in the rat cortex. Surprisingly, we found that central treatment with bovine growth hormone, which is equipotent to rat growth hormone in the rat periphery, failed to rescue cortical neurons following hypoxic ischemic injury. We further investigated the actions of rat and bovine growth hormone on primary neuron-enriched cultures of fetal rat cortex. In agreement with the in vivo treatment studies, rat but not bovine growth hormone rescued neurons from nutrient deprivation-induced cell death (p<0.05). This neuroprotective effect was inhibited by the selective growth hormone receptor antagonist G120D (p<0.001). Furthermore, rat but not bovine growth hormone had trophic effects on uninjured cultures (p<0.001). Immunocytochemistry showed growth hormone receptor on neurons within the neuron-enriched cultures. We show for the first time that the protective and trophic effects of rat growth hormone are mediated via growth hormone receptors on neurons and that the rodent neuronal growth hormone receptor exhibits unique ligand specificity.
authors.affiliation: The Liggins Institute, University of Auckland, Private Bag 92019, Auckland, New Zealand.
authors.forename: Tanja Anna Elisabeth
authors.initials: TA
authors.lastname: Möderscheim
authors.forename: Larissa Joy
authors.initials: LJ
authors.lastname: Christophidis
authors.forename: Chris Edward
authors.initials: CE
authors.lastname: Williams
authors.forename: Arjan
authors.initials: A
authors.lastname: Scheepens
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002545:Brain Ischemia / Q000517:prevention & control; D002417:Cattle; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D013006:Growth Hormone / Q000494:pharmacology; D007150:Immunohistochemistry / Q000379:methods; D007276:Injections, Intraventricular / Q000379:methods; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011986:Receptors, Somatotropin / Q000378:metabolism*
chemical_list: D018696:Neuroprotective Agents; D011986:Receptors, Somatotropin; C073294:growth hormone, bovine; D013006:Growth Hormone; D010751:Phosphopyruvate Hydratase