Time-dependent changes of amino acids in the serum, liver, brain and urineof rats administered with theanine

Time-dependent changes of theanine (gamma-glutamylethylamide) and other ami no acids in various tissues of rats were investigated during the 24 hrs aft er theanine administration. When theanine (4 g/kg of body weight) was intra gastrically administered to rats, the concentrations of theanine in the ser um, liver and brain were significantly increased 1 hr after its administrat ion, and thereafter gradually decreased, but reached the maximum level in t he brain after 5 hrs, Theanine in these tissues had completely disappeared 24 hrs after its administration. In contrast, the administration of theanin e resulted in the concentrations of theanine, urea, ethylamine and glutamic acid in the urine being significantly enhanced. These results suggest that theanine might be degraded via glutamic acid.