title: The IGF-I/IGF-R1 pathway regulates postnatal lung growth and is a nonspecific regulator of alveologenesis in the neonatal rat.
abstract: IGF-I, IGF-II, and the IGF-I receptor are widely distributed throughout the neonatal rat lung on days 4, 7, 10, and 14 of life, with a similar abundance at each of these time points. Injection of 20 μg/g of a truncated soluble IGF-I receptor on days 2 and 5 of life, to decoy ligand away from the endogenous IGF-I receptor, reduced lung weight and lung-to-body weight ratio, reduced lung tissue fraction, and impaired alveolar formation, as assessed by secondary crest formation and mean linear intercepts on day 7 of life. Lung procollagen I content and elastin fiber density were also reduced. Injection of 100 μg/day of neutralizing anti-IGF-I, to prevent IGF-I from binding to the IGF-I receptor, on days 3, 4, and 5 of life reduced tissue fraction and elastin fiber density and impaired alveolar formation on day 6 of life. Both interventions reduced total lung cell and secondary crest cell DNA synthesis and small vessel counts per unit area, but these effects were lost after normalization to the reduced tissue fraction. These findings are consistent with a role for IGF-I binding to the IGF-I receptor in postnatal lung growth and on alveologenesis through a nonspecific positive effect on DNA synthesis. Injection of 100 μg/day of neutralizing anti-IGF-II, to prevent IGF-II from binding to the IGF-I receptor, on days 3, 4, and 5 of life had no effect on total lung cell DNA synthesis per unit area on day 6 of life, and a role for IGF-II in postnatal alveologenesis was not further pursued.
authors: Lung Biology Programme, Physiology & Experimental Medicine, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada.
authors: Jun
authors: J
authors: Li
authors: Azhar
authors: A
authors: Masood
authors: Man
authors: M
authors: Yi
authors: Mandy
authors: M
authors: Lau
authors: Rosetta
authors: R
authors: Belcastro
authors: Julijana
authors: J
authors: Ivanovska
authors: Robert P
authors: RP
authors: Jankov
authors: A Keith
authors: AK
authors: Tanswell
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development; D000906:Antibodies / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis; D007334:Insulin-Like Growth Factor I / Q000276:immunology / Q000494:pharmacology / Q000502:physiology*; D007335:Insulin-Like Growth Factor II / Q000276:immunology; D008168:Lung / Q000254:growth & development* / Q000378:metabolism; D038081:Organogenesis / Q000187:drug effects; D011650:Pulmonary Alveoli / Q000254:growth & development* / Q000378:metabolism; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000502:physiology*
chemical_list: D000906:Antibodies; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D004247:DNA; D017526:Receptor, IGF Type 1
keywords: alveolar formation; growth factors; insulin-like growth factor I; insulin-like growth factor I receptor; lung development