Abstract:

In order to investigate the effect of L-theanine on amino acid (AA) metabolism, growth and development of rats,
weaning rats were administered with L-theanine solution to determine changes in AA compositions in serum and liver.
Sixty-four healthy SD rats with half males and females were randomly divided into 4 groups, which were administered with
L-theanine at the dosages of 0, 50, 200 and 400 mg/(kg·d), respectively. On the 15th day of the experiment, all rats were
sacrificed after 24 h fasting to collect serum and liver for measurement of free AA and ammonia by an AA analyzer. The
results showed that L-theanine increased the daily weight gain, final body weight and glucogenic AAs (Gly, Ser, Ala, Met,
His, Val, Pro, Asp, Asn, Glu and Gln) or facultative glucogenic AAs (Thr, Ile, Phe and Tyr) in the liver of rats. Compared
with the control group, the contents of total essential AAs and some nonessential AAs in the liver of rats administered with
200 mg/(kg·d) L-theanine were increased significantly, and the contents of most AAs in serum were decreased significantly.
L-theanine significantly elevated the concentration of Glu in serum and liver, and the content of ammonia decreased
linearly with L-theanine dose. All results indicated that L-theanine could promote the absorption of dietary AAs, affect AA
concentrations in serum and liver and regulate the growth and development of rats. Meanwhile, L-theanine could increase
Glu concentration and subsequently promote the emission of ammonia to alleviate its harm to the organism.

Key words: L-theanine, rat, amino acid composition, serum, liver