Kinetics of regional blood-brain barrier transport of L-leucine in Brattleboro rats.

The transport of L-leucine across the blood-brain barrier was studied in heterozygous (NON-DI) and homozygous (DI) Brattleboro male rats using the carotid bolus injection technique. Furthermore, general hemodynamic parameters and cerebral blood flow were measured. No significant hemodynamic differences were found between DI and NON-DI rats except for a 22% lower cerebral blood flow in the olfactory bulb of DI rats. The maximum velocity of L-leucine transport (Vmax), the half saturation constant (Km) and the nonsaturable transport constant (KD) were estimated in nine brain regions. The Vmax values of NON-DI rats were by 28% to 64% lower than those of DI rats. The calculated regional Km values of NON-Di rats were by 14% to 58% lower. These differences were most pronounced in hippocampus and hypothalamus. The results support the suggestion that endogenous vasopressin may alter the large neutral amino acid transport across the blood-brain barrier.