HIGH AFFINITY UPTAKE SYSTEMS FOR TAURINE IN TISSUE SLICES AND SYNAPTOSOMAL FRACTIONS PREPARED FROM VARIOUS REGIONS OF THE RAT CENTRAL NERVOUS SYSTEM. CORRECTION OF TRANSPORT DATA BY DIFFERENT EXPERIMENTAL PROCEDURES

Abstract— —The uptake of taurine into tissue slices of specific regions of the rat central nervous system (CNS) was compared with the uptake of taurine into synaptosomal fractions prepared from the corresponding regions. Two different techniques for performing control experiments were also compared: procedure I, correction for the uptake of taurine obtained from duplicate incubations but at 2°c and procedure II, correction of taurine uptake into extracellular or extrasynaptosomal space measured by inulin uptake experiments plus correction for diffusion (non-saturable) processes.
Kinetic analyses of the uptake data in tissue slices utilizing the procedure I correction technique indicate that six regions of the rat CNS (spinal cord, diencephalon, cortex, striatum, hippocampus, and midbrain) possess high affinity uptake systems (K_m values approx 60 μM or less). The K_m value for the cerebellum (105.4 ± 15.7 μM) is intermediate between a high and low affinity uptake system while the K_m value for the pons-medulla (210.0 12.4 μM) is considered to be low affinity. When procedure II techniques were utilized for correcting the uptake data all eight regions demonstrated high affinity uptake systems (11.8–73.2μM).
Synaptosomal fractions prepared from the spinal cord, pons-medulla, diencephalon, and midbrain demonstrate high affinity uptake systems (procedure I) for taurine (10.3–47.2 μM) while the hippocampus, cortex, striatum, and cerebellum have intermediate (but still high affinity) values (59.4–96.4 μM). High affinity uptake systems (8.2–79.8 μM) were obtained for all eight regions of the rat CNS when procedure II was utilized for correction of the data.