title: Intracellular metabolism of 2',3'-dideoxynucleosides in duck hepatocyte primary cultures.
abstract: The intracellular fate of the potent duck hepatitis B virus (DHBV) inhibitor 2,6-diaminopurine 2',3'-dideoxyriboside (ddDAPR), its deamination product 2',3'-dideoxyguanosine (ddG), and the less effective DHBV-inhibitor 2',3'-dideoxycytidine (ddC) was investigated in duck hepatocyte primary cultures. After a 1-min exposure of [3H]ddDAPR to duck blood, 95% of the compound was converted to ddG. Similarly, [3H]ddDAPR was converted rapidly to ddG in duck hepatocyte primary cultures, with ddG exhibiting resistance to further catabolism. The major pathway of ddG utilization in these cells was phosphorylation, yielding a concentration of 2.1 and 1.9 microM total ddG nucleotides after 5 and 26 hr, respectively, of exposure to 4 microM ddG. Removal of exogenous ddG led to a rapid (T1/2 = 1.6 hr) decrease in the total intracellular ddG nucleotide pools. Duck hepatocytes treated with 4 microM ddC exhibited a time-dependent accumulation of ddC nucleotides, culminating in a maximum intracellular total ddC nucleotide concentration of 1.4 microM after 24-26 hr. The intracellular total ddC nucleotide level decreased with a T1/2 of 4.4 hr following the removal of exogenous ddC. The formation of ddC nucleotides was reduced in the presence of excess 2'-dideoxycytidine implicating deoxycytidine kinase in the initial step of ddC phosphorylation. A 25-fold excess of 2'-deoxycytidine had no effect on ddG phosphorylation in duck hepatocytes. However, a 92% inhibition of ddG nucleotide formation occurred in duck hepatocytes treated for 5 hr with 4 microM [3H]dG + 100 microM adenosine in the presence of the adenosine deaminase inhibitor 2'-deoxycoformycin, suggesting that, in these cells, adenosine kinase is involved in the ddG phosphorylation process.
authors.affiliation: Department of Medical Microbiology and Infectious Diseases, University of Alberta, Edmonton, Canada.
authors.forename: T E
authors.initials: TE
authors.lastname: Kitos
authors.forename: D L
authors.initials: DL
authors.lastname: Tyrrell
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000097:blood; D000998:Antiviral Agents / Q000494:pharmacology; D002478:Cells, Cultured; D003841:Deoxycytidine / Q000494:pharmacology; D016048:Dideoxyadenosine / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism / Q000494:pharmacology; D015224:Dideoxynucleosides / Q000378:metabolism; D004372:Ducks / Q000378:metabolism*; D015611:Hepatitis B Virus, Duck / Q000187:drug effects; D008099:Liver / Q000378:metabolism*; D010766:Phosphorylation; D016047:Zalcitabine / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000998:Antiviral Agents; D015224:Dideoxynucleosides; D003841:Deoxycytidine; C052692:2,6-diaminopurine 2',3'-dideoxyriboside; D016048:Dideoxyadenosine; D016047:Zalcitabine; C050220:2',3'-dideoxyguanosine