TY - JOUR
T1 - Glucagon receptor agonists and antagonists affect the growth of the chick eye
T2 - A role for glucagonergic regulation of emmetropization?
AU - Vessey, Kirstan A.
AU - Lencses, Kathy A.
AU - Rushforth, David A.
AU - Hruby, Victor J.
AU - Stell, William K.
PY - 2005/11
Y1 - 2005/11
N2 - PURPOSE. In chicks, plus defocus retards eye growth, thickens the choroid, and activates glucagonergic amacrine cells, probably releasing glucagon. Glucagon receptor antagonists (expected to inhibit compensation to plus defocus) and agonists (expected to block myopia induction by form deprivation) were administered to eyes of chicks, to test the hypothesis that glucagon mediates the induction of changes in eye growth by plus defocus. METHODS. Seven-day-old (P7) chick eyes were injected intravitreally with peptides at concentrations of ∼10-9 to 10-5 in 20 μL (injection volume). The glucagon-receptor antagonists [des-His1,des- Phe6,Glu 9]-glucagon-NH2 (des-Phe6-antagonist) and [des-His1,Glu9]-glucagon-NH2 (Phe 6-antagonist) were administered daily for 4 to 5 days to plus-defocused eyes. Agonists (porcine glucagon-[1-29] and [Lys 17,18,Glu21]-glucagon-NH2) were monocularly administered daily for 5 days to form-deprived eyes. The contralateral eye remained open and received saline. After treatment, eyes were refracted, measured, and examined for histologic changes. MESULTS. The Phe 6-antagonist at 10-5 M (in the syringe) inhibited changes in both refractive error and axial length compensation induced by +7-D lens wear; however, des-Phe6-antagonist (10-5 M) had weak, inconsistent effects and did not antagonize the action of exogenous glucagon. Glucagon prevented ocular elongation and myopia and induced choroidal thickening in form-deprived eyes. [Lys17,18,Glu21]-glucagon-NH 2 had little effect at 10-7 M, but at 10-6 to 10-5 M altered rod structure and inhibited eye growth. CONCLUSIONS. Exogenous glucagon inhibited the growth of form-deprived eyes, whereas Phe 6-antagonist inhibited compensation to plus defocus, as might be expected if glucagon is an endogenous mediator of emmetropization. The reason for the failure of des-Phe6-antagonist to counteract the effects of exogenous glucagon requires further investigation.
AB - PURPOSE. In chicks, plus defocus retards eye growth, thickens the choroid, and activates glucagonergic amacrine cells, probably releasing glucagon. Glucagon receptor antagonists (expected to inhibit compensation to plus defocus) and agonists (expected to block myopia induction by form deprivation) were administered to eyes of chicks, to test the hypothesis that glucagon mediates the induction of changes in eye growth by plus defocus. METHODS. Seven-day-old (P7) chick eyes were injected intravitreally with peptides at concentrations of ∼10-9 to 10-5 in 20 μL (injection volume). The glucagon-receptor antagonists [des-His1,des- Phe6,Glu 9]-glucagon-NH2 (des-Phe6-antagonist) and [des-His1,Glu9]-glucagon-NH2 (Phe 6-antagonist) were administered daily for 4 to 5 days to plus-defocused eyes. Agonists (porcine glucagon-[1-29] and [Lys 17,18,Glu21]-glucagon-NH2) were monocularly administered daily for 5 days to form-deprived eyes. The contralateral eye remained open and received saline. After treatment, eyes were refracted, measured, and examined for histologic changes. MESULTS. The Phe 6-antagonist at 10-5 M (in the syringe) inhibited changes in both refractive error and axial length compensation induced by +7-D lens wear; however, des-Phe6-antagonist (10-5 M) had weak, inconsistent effects and did not antagonize the action of exogenous glucagon. Glucagon prevented ocular elongation and myopia and induced choroidal thickening in form-deprived eyes. [Lys17,18,Glu21]-glucagon-NH 2 had little effect at 10-7 M, but at 10-6 to 10-5 M altered rod structure and inhibited eye growth. CONCLUSIONS. Exogenous glucagon inhibited the growth of form-deprived eyes, whereas Phe 6-antagonist inhibited compensation to plus defocus, as might be expected if glucagon is an endogenous mediator of emmetropization. The reason for the failure of des-Phe6-antagonist to counteract the effects of exogenous glucagon requires further investigation.
UR - http://www.scopus.com/inward/record.url?scp=27744518106&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=27744518106&partnerID=8YFLogxK
U2 - 10.1167/iovs.04-1026
DO - 10.1167/iovs.04-1026
M3 - Article
C2 - 16249465
AN - SCOPUS:27744518106
SN - 0146-0404
VL - 46
SP - 3922
EP - 3931
JO - Investigative Ophthalmology and Visual Science
JF - Investigative Ophthalmology and Visual Science
IS - 11
ER -