SIMULTANEOUS DETERMINATION OF 6-THIOGUANINE AND METHYL 6-MERCAPTOPURINE NUCLEOTIDES OF AZATHIOPRINE IN RED-BLOOD-CELLS BY HPLC

6-thioguanine (6-TGN) and methyl 6-mercaptopurine nucleotides (Me6-MPN s) are the two major metabolites found in erythrocytes after administr ation of azathioprine. In an attempt to understand the role of these m etabolites in the pharmacologic and toxic activity of thiopurines, we have developed a HPLC method for the simultaneous determination of 6-T GNs and Me6-MPNs in erythrocytes. A simple and rapid treatment procedu re based on deproteinization by perchloric acid with dithiothreitol is described, The nucleotides were hydrolyzed to their own bases by heat ing the sample for 45 min at 100 degrees C. During acid hydrolysis MeG -MP was converted into a compound analyzed on a Purospher RP18-e colum n with 0.02 mol/L dihydrogenophosphate buffer-methanol as eluents. Wit h this procedure, mean recoveries of 73.1% and 84.0% for 6-TGN and Me6 -MPN derivatives, respectively, were found.