Transport of Glycine From the Cerebrospinal Fluid

USING automated chromatographic techniques, it has been possible to determine with precision in several mammalian species that the concentrations of many amino acids are considerably less in cerebrospinal fluid (CSF) than in plasma.¹⁻³There is accumulating evidence that the low CSF to plasma ratios for many solutes are maintained in part by uphill transport from CSF to blood.⁴⁻⁶Such low CSF to plasma ratios have been considered to play a role in the regulation of tissue concentrations of these substances through a sink action.⁷The need for understanding of the mechanisms which regulate amino acid concentrations in various portions of the nervous system is emphasized by the fundamental role which certain amino acids are thought to play in synaptic transmission, as well as the common occurrence of mental retardation in conjunction with aminoacidopathies. The CSF concentration of glycine is one twentieth of that in