Abstract
It was already reported that the hepatic tyrosine transaminase (TTA) activity(L-tyrosine 2-oxaloglutarate aminotransferase E.C.2.6.1.5) in tumorbearing animals is incresed about 2-fold above the normal level. When mice were employed as experimental animals, TTA activity is much more strongly induced by hydrocortisone than that of rats, while not by tryptophan. Therefore the transplanatation effect of Ehrlich's ascites tumor and Sarcoma 180 on the TTA induction was observed in mice. The hepatic TTA activity gradually rised from the 6th day after intraperitoneal inoculation of these tumor cells in contrast with the decrease of contents of hepatic vitamin B_6 or pyridoxal phosphate. The rise finally attained the 8-fold increase above the basal level on the 11th day while the rise of aspartate transaminase activity was shown to be only 2-fold high and no rise of alanine transaminase was shown. Although the increase of TTA activity was observed throughout tumor growth, the maximal activity of the enzyme was observed when the decrease of numbers of tumor cells(cell destruction)appeared. The supernatant of ascites by centrifugation caused an appreciable increase of hepatic TTA activity 4 hours after intrapritoneal injection into normal rats, while no increase in the adrenalectomized rats. It was found that some of the factors in ascites for elevation of TTA activity were thermostable and nondializable. (Received Jan. 13,1971)
