Studies on the relationship between increased adenylic acid deaminase activity and changes in nuclear RNA metabolism in rat liver caused by thioacetamide.

The purpose of this study was to determine whether increases in AMP1 deaminase activity caused by TA injections were mediated by RNA biosynthesis. Multiple TA injections (50 mg/kg body weight) resulted in 2to 3-fold increases in AMP deaminase activity, but simultaneous injection of Act. D (120 Mg/kg body weight) or 5-FU (30 mg/kg body weight) with TA caused no interference with this increase. AMP deaminase was activated in vitro with ATP; however, in the presence of ATP the enzyme activity of TA-injected animals was twice that of saline controls, and these increases still were not inhibited by Act. D or 5-FU. On the other hand, Act. D inhibited, but 5-FU enhanced, the increases in nucleoli diameters caused by TA injections. Neither 1 nor 4 injections of Act. D alone changed the concentration of NNN2 or "nucleolar" RNA, and incorpora tion of orotic acid-6-14C into these fractions was not altered. When Act. D was injected simultaneously with TA, it did not inhibit increases in "nucleolar" RNA content nor increases in the