EFFECT OF THIOACETAMIDE ON ADENYLIC ACID DEAMINASE ACTIVITY AND NUCLEAR RIBONUCLEIC ACID METABOLISM IN RAT LIVER.

Abstract

Thioacetamide was administered to rats to determine whether increases in hepatic adenylic acid (AMP) deaminase activity could be achieved in shorter time intervals than had been previously observed with azo dyes (23). Thioacetamide was added to a semisynthetic diet at 0.033% or 0.066% and was fed to rats for 12 weeks. Within 2 weeks hepatic AMP deaminase activity was significantly elevated and remained elevated throughout 12 weeks. When thioacetamide was injected intraabdominally once daily for 9 days at 50 mg/kg body weight, hepatic AMP deaminase activity was significantly elevated after 3 injections. This regimen also caused increases in the amount of nuclear ribonucleic acid (RNA), and in the diameters of nuclei and nucleoli. Nuclear RNA was subfractionated into “non-nucleolar” nuclear (NNN) and “nucleolar” fractions and it was observed that nearly all the increase in nuclear RNA occurred in the “nucleolar” fraction. The rates at which orotic acid-6-14C was incorporated into these 2 fractions indicated that 3 injections of thioacetamide increased “nucleolar” RNA synthesis; whereas 3, 6, or 9 injections increased NNN RNA synthesis.