Uptake and K+-stimulated release of [14C]glycine from frog retinal synaptosomal fractions.
The uptake of [14C]glycine and the effect of depolarizing potassium concentrations on its release was investigated in the whole frog retina and its synaptosomal fractions. The uptake of [14C]glycine in retina and synaptosomal fractions was found to be saturable as well as energy and Na+-dependent. The Km value for glycine uptake was found to be 46 microM for P2 fraction and 100 microM for P1 fraction, with a Vmax of 3.5 and 3.8 nmol/mg protein/min respectively. The release of [14C]glycine from P1 and P2 synaptosomal fractions was markedly increased by raising potassium concentration in the medium, in a partially Ca2+-dependent manner. Evoked glycine release was 50% reduced when calcium was omitted from the medium. The K+-stimulated release of glycine from P2 fraction was significantly reduced in the presence of TTX. The cellular origin of the P1 and P2 synaptosomal fractions releasing glycine is discussed.
Salceda
R
R
Dept. de Neurociencias, Universidad Nacional Autónoma de México, D.F., México.
D000818:Animals; D002118:Calcium / Q000502:physiology; D005998:Glycine / Q000378:metabolism*; D008029:Lighting; D011188:Potassium / Q000494:pharmacology*; D011898:Ranidae / Q000378:metabolism* / Q000502:physiology; D012160:Retina / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology
D013779:Tetrodotoxin; D011188:Potassium; D002118:Calcium; D005998:Glycine