2'-deoxycoformycin toxicity in murine spleen lymphocytes
Earle, M.F.; Glazer, R.I.
Molecular Pharmacology 23(1): 165-170
1983
ISSN/ISBN: 0026-895X PMID: 6602939 Document Number: 202911
To investigate the direct lymphocytic toxicity of the adenosine deaminase inhibitor, 2'-deoxycoformycin (dCF), an in vitro model system using concanavalin A-stimulated mouse spleen lymphocytes was utilized. When lymphocytes were incubated for 24 or 66 h with 10-8-10-4 M dCF added 30 min prior to addition of mitogen, a time- and dose-dependent inhibition of DNA and RNA synthesis occurred. The IC50 values for DNA and RNA synthesis and adenosine deaminase activity 66 h after drug exposure were 10-6 M, 3 .times. 10-6 M and 3 .times. 10-9 M, respectively. When lymphoblastogenesis was measured 24 h after the addition of 10-4 M dCF, DNA and RNA syntheses were inhibited 10 and 30%, respectively, despite the same marked inhibition of adenosine deaminase activity observed at 66 h. Following 66 h of treatment with 10-6 M dCF, methylation of RNA and DNA were not affected; a moderately higher degree of DNA, but not RNA, methylation was noted following exposure to 10-4 M dCF. Measurement of cellular ribonucleotide levels 24 and 66 h after drug exposure revealed a dose-dependent reduction in nucleoside mono- and triphosphates. A 2- to 2.5-fold elevation in IMP levels at 10-6 M dCF and 50-100% reduction in IMP levels at 10-4 M dCF were observed at both 24 and 66 h after treatment. Levels of dATP were not significantly altered 24 and 66 h after treatment with dCF. These data suggest that inhibition of nucleic acid synthesis by dCF is not dose-related to the inhibition of adenosine deaminase, that DNA and RNA methylation and dATP levels are unaffected and that changes in nucleotide levels accompany drug-mediated lymphocytic toxicity.