title: Opposite effects of glucagon and insulin on compensation for spectacle lenses in chicks.
abstract: OBJECTIVE
  Chick eyes compensate for the defocus imposed by positive or negative spectacle lenses. Glucagon may signal the sign of defocus. Do insulin (or IGF-1) and glucagon act oppositely in controlling eye growth, as they do in metabolic pathways and in control of retinal neurogenesis?
  
  
  METHODS
  Chicks, wearing lenses or diffusers or neither over both eyes, were injected with glucagon, a glucagon antagonist, insulin, or IGF-1 in one eye (saline in the other eye). Alternatively, chicks without lenses received insulin plus glucagon in one eye, and either glucagon or insulin in the fellow eye. Ocular dimensions, refractive errors, and glycosaminoglycan synthesis were measured over 2 to 4 days.
  
  
  RESULTS
  Glucagon attenuated the myopic response to negative lenses or diffusers by slowing ocular elongation and thickening the choroid; in contrast, with positive lenses, it increased ocular elongation to normal levels and reduced choroidal thickening, as did a glucagon antagonist. Insulin prevented the hyperopic response to positive lenses by speeding ocular elongation and thinning the choroid. In eyes without lenses, both insulin and IGF-1 speeded, and glucagon slowed, ocular elongation, but glucagon and insulin each increased the rate of thickening of the crystalline lens. When injected together, insulin blocked choroidal thickening by glucagon, at a dose that did not, by itself, thin the choroid.
  
  
  CONCLUSIONS
  Glucagon and insulin (or IGF-1) cause generally opposite modulations of eye growth, with glucagon mostly increasing choroidal thickness and insulin mostly increasing ocular elongation. These effects are mutually inhibitory and depend on the visual input.
authors.affiliation: Department of Biology, City College, CUNY, New York, New York 10031, USA. xiaoying@sci.ccny.cuny.edu
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Zhu
authors.forename: Josh
authors.initials: J
authors.lastname: Wallman
mesh_terms: D000818:Animals; D000867:Anterior Chamber / Q000187:drug effects; D002645:Chickens; D002829:Choroid / Q000187:drug effects / Q000378:metabolism; D003261:Contact Lenses; D004195:Disease Models, Animal; D004338:Drug Combinations; D005123:Eye / Q000254:growth & development*; D005934:Glucagon / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006025:Glycosaminoglycans / Q000096:biosynthesis; D006727:Hormone Antagonists / Q000494:pharmacology; D006728:Hormones / Q000494:pharmacology*; D006956:Hyperopia / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007267:Injections; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007908:Lens, Crystalline / Q000187:drug effects / Q000378:metabolism; D009216:Myopia / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D012590:Sclera / Q000378:metabolism; D012683:Sensory Deprivation
chemical_list: D004338:Drug Combinations; D006025:Glycosaminoglycans; D006727:Hormone Antagonists; D006728:Hormones; D007004:Hypoglycemic Agents; D007328:Insulin; C080071:glucagonamide, desHis(1)-Glu(9)-; D007334:Insulin-Like Growth Factor I; D005934:Glucagon
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