Trh in the rat cerebellum: II. Uptake by cerebellar slices.

We investigated the in vitro uptake of exogenous TRH by rat cerebellar slices. TRH was found to be taken up via a process sharing many of the properties of a high affinity transport system, viz: (1) saturation kinetics; (2) high affinity kinetic constants (Km1 = 1.06 X 10(-5) M, Km2 = 5.6 X 10(-6) M); (3) temperature sensitivity (Q10 = 1.48); (4) dependency on the sodium concentration in the incubation medium; and (5) tissue/medium ratios greater than 1. After 60 min of incubation at 27 degrees C in the presence of Bacitracin, the tissue/medium ratio was 5:1. Under these conditions 70% of the total label was recovered as [3H-Pro]TRH. These findings demonstrated the existence of removal mechanisms for TRH in the cerebellum and gave further support to the hypothesis that TRH plays a functional role removal mechanisms for TRH in the cerebellum and gave further support to the hypothesis that TRH plays a functional role in this extrahypothalamic brain region.