Temperature dependence of amino acid transport in brain slices.

A decrease in amino acid influx and exit in incubated slices when the temperature was lowered from 37 to 20°C was observed with all 16 amino acids examined at two concentrations (1 mM and 10 μM). The temperature dependence of cellular amino acid influx observed in slices in vitro contrasts with the absence of temperature dependence of capillary amino acid influx in the brain in vivo that we recently reported. The temperature effects in slices varied some-what among the various amino acid transport classes. With some amino acids (Phe, Val, Tyr, Asp, Glu), especially at lower concentrations, the greater inhibition of exit than of uptake resulted in an actual increase in tissue amino acid uptake at lower temperatures in long-term experiments. The results indicate heterogeneity in the effect of temperature on the various transport classes and show a difference between capillary and cellular amino acid transport in the brain.