Abstract

PD 116124 (8-amino-2'-nordeoxyguanosine; 2,8-diamino-1,9-dihydro-9- ([2-hydroxy-1-(hydroxymethyl)ethoxy]methyl)-6H-purin-6-one) is a competitive, reversible inhibitor of human purine nucleoside phosphorylase with an apparent inhibition constant of 0.41 microM. In a cell line system using human MOLT-4 and CEM T lymphoblasts and human MGL-8 and NC-37 B lymphoblasts, PD 116124 failed to inhibit [3H]thymidine uptake at concentrations up to 500 microM. However, in the presence of 10 microM 2'-deoxyguanosine (dGuo), a noninhibitory dGuo concentration by itself, PD 116124 produced potent inhibition of growth of both T cell lines but not of either B cell line. Significant elevation of intracellular 2'-deoxyguanosine triphosphate was observed in both inhibited T cell lines but not in either B cell line. Greater and more sustained accumulation of 2'-deoxyguanosine triphosphate was observed in T lymphoblasts cultured with PD 116124 plus dGuo than with dGuo only. PD 116124 was only weakly inhibitory in human mixed lymphocyte cultures (IC50 approximately equal to 1420 microM), but in the presence of 10 microM dGuo, the IC50 for PD 116124 was reduced to 108.7 microM. Administration of PD 116124 p.o. to normal male Wistar rats caused dose-dependent elevation of plasma inosine up through 500 mg/kg. Maximal inosine elevation occurred at 30 min after dosing, and elevation was significant even 24 hr after dosing. Guanosine was also elevated, although not in a dose-dependent manner. Administration of PD 116124 i.v. produced marked and statistically significant elevation of both inosine and guanosine.(ABSTRACT TRUNCATED AT 250 WORDS)