Abstract
The effects of rhatannin (condensed tannin) purified from Rhei Rhizoma on urea nitrogen and amino acid concentrations and on the activities of various enzymes concerned with the urea cycle and amino acid metabolism in the rat were investigated. Rhatannin significantly reduced the blood urea nitrogen (BUN) concentration by 16-31% at 4-8 h after intraperitoneal administration. The reduction of BUN concentration was proportional to that of urea nitrogen concentration in the liver. The activities of five urea cycle enzymes were not affected by the administration of rhatannin. On the other hand, the concentrations of eleven amino acids (Gln, Ala, Gly, Ser, Glu, Lys, Met, Pro, Orn, Cit, Arg) in the plasma were decreased. In addition, the concentrations of three amino acids (Gln, Glu, Asp) in the liver were decreased and the Gly concentration was increased. The glutamine synthetase activity in the liver was significantly increased by 52-57% at 2-4 h, while glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, glutamate dehydrogenase, and glutaminase activities were not altered. Ammonia concentration in the hepatic vein was reduced at 4-8 h prior to the reduction of ammonia concentration in the portal vein.
