Activities of purine catabolism related enzymes in zinc deficiency: relationship to T-lymphocyte dysfunction and hyperammonemia

The activities of liver, muscle, and red blood cell enzymes involved in the degradation of purine were assayed in zinc deficient (ZD), pair-fed control (PF) and ad libitum-fed control (Ad lib) rats. Diets (1.5 ppm of zinc in ZD diet and 110 ppm in control diet) were fed to rats for 6 weeks after which they were sacrificed and tissues isolated for several assays. Results indicated a significant increase in the concentration of plasma NH3 (P less than .0005) and uric acid (P less than .05), and a decrease in the concentration of blood urea nitrogen (BUN) (P less than .025) in ZD rats compared to both control groups. The activities of liver and red blood cell (RBC) nucleoside phosphorylase (NPase) were lower (P less than .025) in ZD rats. Activity of 5'adenosine monophosphate deaminase (AMPDA) was higher in liver (P less than .0001) and muscle (P less than .01) in ZD groups vs. controls. Activity of hypoxanthine polyribosyl transferase (HPRT) in liver was higher (P less than .005) in ZD group compared to controls. The present findings could be viewed from two aspects: first, they provide an insight into the specific role of zinc on T-lymphocyte function which is believed to be mediated by the regulatory effect of zinc on the enzyme nucleoside phosphorylase and, second they provide a possible mechanism for hyperammonemia observed in zinc deficient human subjects and experimental animals.