[Effect of diketopiperazine on mouse liver regeneration following partial hepatectomy]

Inhibition of serine-hydroxymethyl transferase activity by dimer of cycloserine--diketopiperazin (DP) was studied in vivo in mice liver tissue. DP (2500 mg and 4000 mg per kg of body weight) caused a decrease in the enzyme activity by 14% and 30%, respectively, within 2 hrs after intraperitoneal administration into the animals. Complete reactivation of the enzyme was observed in presence of pyridoxal phosphate added into the experimental samples. DP inhibited the rate of mice liver regeneration after partial hepatectomy, if it was administered separately or in combination with methotrexate within 8 days before and 4 days after the operation. The decreased rate of the tissue regeneration occurred simultaneously with a distinct decrease in the serine-hydroxymethyl transferase activity in vivo. Methotrexate did not affect the liver tissue regeneration after hepatectomy. A method is described for estimation of the serine-hydroxymethyl transferase activity in tissue extracts in presence of partially purified preparation of 5,10-methylene-H4-folate-dehydrogenase.