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Pharmacological properties of glycine uptake in the developing rat retina
1Instituto de Fisiología Celular, Departamento Neurociencias, Universidad Nacional Autónoma de México, Apdo. Postal 70-253, C.P. 04510 México D.F., Mexico. rsalceda@ifc.unam.mx
Insights
Glycine transport in the rat retina shows developmental changes, with a high-affinity system present. This suggests specific glycine transporter roles in retinal development and function.
Area of Science:
- Neuroscience
- Biochemistry
- Developmental Biology
Background:
- Glycine is a key neurotransmitter in the central nervous system.
- Glycine transporters (Glyts) regulate glycine levels.
- Understanding glycine transport is crucial for retinal function and development.
Purpose of the Study:
- To pharmacologically characterize glycine transport in the developing rat retina.
- To identify the types and properties of glycine transporters present.
- To elucidate the role of glycine transport in retinal maturation.
Main Methods:
- Uptake of 3H-glycine in rat retinal tissue at various postnatal ages.
- Kinetic analysis to determine transporter affinity (Km) and stoichiometry (Hill coefficient).
- Inhibition studies using specific transporter blockers (sarcosine, ALX5407, amoxapine) and signaling pathway modulators (staurosporine, phorbol ester).
Main Results:
- Glycine uptake increased during the first two postnatal weeks, peaking at 12 days, then declining to adult levels.
- A Na+-dependent, high-affinity glycine transport system (Km = 100 microM) was identified.
- Sarcosine and ALX5407 inhibited uptake by 40-50%, while amoxapine showed differential inhibition in immature (70%) and adult (40%) retina.
- Glycine uptake was insensitive to staurosporine and phorbol ester, suggesting Glyt1 transporter localization in nerve terminals.
Conclusions:
- The Glyt1 transporter is likely concentrated in retinal nerve terminals.
- Evidence suggests the presence of Glyt2 and/or other glycine transporter isoforms in the retina.
- These transporters play a significant role in rat retinal development.
Abstract:
A pharmacological characterization of glycine transport was performed in the rat retina at different postnatal ages. The uptake of 3H-glycine increased during the first 2 weeks of postnatal age, reaching maximum values at 12 days; then it decreased sharply to the adult values. We found a Na+ -dependent and high-affinity transport system with a Km of 100 microM. The Na+ Hill coefficient for glycine uptake was 1.76 +/- 0.07. Although glycine uptake was insensitive to staurosporine and phorbol ester, it was reduced 40-50% by sarcosine and ALX5407. Besides, amoxapine inhibited glycine uptake by 40 and 70% in adult and immature retina, respectively. These results suggest that the Glyt1 transporter was concentrated in the nerve terminals. In addition to the presence of Glyt1 in the retina, our results provided evidence of the occurrence of Glyt2 and/or another isoform of glycine transporter, which might have had a role in the retina development.
