Pharmacological properties of glycine uptake in the developing rat retina

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 μM. 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.