Abstract
The mechanism by which rhatannin (condensed tannin purified from Rhei Rhizoma) produces a prolonged decrease in plasma amino acids in the postabsorptive state was investigated in vivo by measuring the incorporation of [14C] phenylalanine (Phe) into proteins in serum, liver, kidney and muscle. Enhanced incorporation into serum proteins was observed 4 to 8 h after the intraperitoneal administration (12.5 mg/kg body weight), and the maximal enhancement was observed 6 h after the treatment. Incorporations into other proteins did not change. Further, a fluorogram of the polyacrylamide gel electrophoretic pattern of serum obtained from rats after rhatannin treatment revealed incorporation of the labeled amino acid into protein (s) which corresponded to albumin in terms of electrophoretic mobility. Incorporation of [3H] phenylalanine after a 20 min in vivo labeling 6 h after rhatannin treatment was enhanced in hepatic microsomal and mitochondrial fractions. In addition, stimulated incorporation of [3H] orotic acid into rat hepatic nuclear and cytoplasmic ribonucleic acids (RNA) was observed after rhatannin treatment and the maximal enhancements were achieved at 6 h. Thus, the decrease of plasma amino acid level 4 to 8 h after rhatannin treatment may be due in part to the increased removal of amino acids by the liver, although the underlying mechanisms of enhancement of the syntheses of hepatic protein and RNA in rhatannintreated rats remain obscure.
