RESUMO
Methyl (S)-4-(6-amino-9H-purin-9-yl)-2-hydroxybutanoate (DZ2002) is a potent reversible inhibitor of S-adenosyl-L-homocysteine hydrolase (SAHH). Due to its ester structure, DZ2002 is rapidly hydrolyzed in rat blood to 4-(6-amino-9H-purin-9-yl)-2-hydroxybutyric acid (DZA) during and after blood sampling from rats; this hampers accurate determination of the circulating DZ2002 and its acid metabolite DZA in rats. To this end, a method for determining the blood concentrations of DZ2002 and DZA in rats was developed by using methanol to immediately deactivate blood carboxylesterases during sampling. The newly developed bioanalytical assay possessed favorable accuracy and precision with lower limit of quantification of 31 nM for DZ2002 and DZA. This validated assay was applied to a rat pharmacokinetic study of DZ2002. After oral administration, DZ2002 was found to be extensively converted into DZA. The level of systemic exposure to DZ2002 was significantly lower than that of DZA. The apparent oral bioavailability of DZ2002 was 90％–159％. The mean terminal half-lives of DZ2002 and DZA were 0.3–0.9 and 1.3–5.1 h, respectively. The sample preparation method illustrated here may be adopted for de-termination of other circulating ester drugs and their acid metabolites in rodents.
RESUMO
Objective To study the genome DNA methylation in rheumatoid arthirits(RA)and the re- lated factors of DNA methylation.Methods Twenty-first cases with RA and 20 controls were recruited to par- ticipate the study.Plasma Hcy,SAM,SAH,the MTHFR gene C677T polymorphism and the expression of LFA-1 in CD4~+T cells was measured in all patients and controls.Results①The SAM levels were lower sig- nificantly in RA groups than in controls.The SAH levels were higher significantly in RA groups than in con- trols.②There was significant inverse correlation between plasma Hcy level and SAM level(r=-0.932,P＜0.01). There was significant positive correlation between plasma Hcy level and SAH level(r=0.924,P＜0.01).③The expression of LFA-1 in CD4~+T cells was higher significantly in RA groups than in controls.There was a signif- icant positive correlation between LFA-1 expression level and Hcy level(r=0.557,P＜0.01),a significant in- verse correlation between LFA-1 expression level and SAM level(r=-0.651,P＜0.01).④The MTHFR gene mu- tation lead to dramatically increase of Hcy,SAH level and the expression of LFA-1 level in CD4~+T cells and genome DNA hypomethylation.Conclusion①Hypomethylation of genome DNA is found in most RA pa- tients.②The factors associated with genome DNA hypomethylation include MTHFR gene mutation and hyper- homocysteinemia.③The expression of LFA-1 in CD4~+ T cells is higer in RA groups than in controls,which re- lates to the DNA methylation level and the MTHFR gene C677T polymorphism.