Glycine stimulation of glutamate binding to chick retinal pigment epithelium |
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Authors: | A M López-Colomé G Fragoso |
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Institution: | (1) Instituto de Fisiología Celular, U.N.A.M., Apartado Postal 70-253, 04510 México, D.F., México |
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Abstract: | The effect of glycine (Gly) and taurine (Tau) on the biochemical and pharmacological properties of 3H]l-glutamate (3H] Glu) binding to membranes from primary cultures of chick retinal pigment epithelium (RPE), as well as from intact tissue during development was studied. Gly and Tau increase Bmax of 3H]Glu binding to a high affinity site (KB=300 nM) in membranes from 16 days in vitro (immature) cultures; additionally, Gly discloses a low affinity Glu-binding site (KB=970 nM) at this stage. In membranes from 25 days in vitro (mature) cultures, the high affinity site is no longer present and Tau has no effect on Glu-binding; Gly still stimulates binding to the low affinity site by four fold, with an EC50=200 M. Pharmacological profile using specific excitatory amino acid (EAA) receptor agonists and antagonists suggests that at 16 days in vitro Glu binds preferentially to metabotropic Glu receptors (mGluRs), and at 25 days in vitro to ionotropic receptors different from neuronal ones. The stimulatory effect of Gly and Tau was also observed in intact RPE, and decreased with increasing embryonic age. Glu binding was also stimulated in membranes from chick retina, but not in those from rat brain. Results support the possibility of EAA participation in several aspects of RPE physiology, including phagocytosis and cell division.Abbreviations L-Glu
l-glutamate
- QA
quisqualate
- KA
kainate
- NMDA
N-methyl-d-aspartate
- trans-ACPD
(±) 1-aminocyclopentane-trans-1,3-dicarboxylic acid
- D-AP5
d-2-amino-5-phosphonopentanoic acid
- L-AP4
l-2-amino-4-phosphonobutyric acid
- L-AP3
l-2-amino-3-phosphonopropionic acid
- CNQX
6-cyano-7-nitroquinoxaline-2,3-dione
- (+)MCPG
(+) -methyl-4-carboxyphenyl-glycine
- DHPG
(RS) 3,5-dihydroxyphenyl-glycine
- CPP
3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid
- MK-801
(+)-5-methyl-10, 11-dihydro-5H-dibenzo a.d.] cyclohepten-5, 10-imine
- PIP2
phosphatidyl inositol bisphosphate
- ED
embryonic day
- DIV
days in vitro
- RPE
retinal pigment epithelium
- EAA
excitatory amino acids |
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Keywords: | Glutamate receptors retina cell culture glycine taurine |
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