The distribution pattern of intravenous [14C] artesunate in rat tissues by quantitative whole-body autoradiography and tissue dissection techniques

Quantitative whole-body autoradiography (QWBA) and liquid scintillation counting (LSC) have been conducted to determine the metabolic profiles and tissue distribution of [14C] labeled artesunate (AS) injection in rats. The QWBA technique showed more accurate results in the quantification of radioactivity in 40 organs and tissues, compared to 19 organs with the LSC technique. The benefit of QWBA was especially apparent on measurements of bile, bone marrow, and gland organs; however, the LSC method produced more relevant findings than QWBA. Particularly, the LSC method allowed access to the following distribution patterns that were unavailable via QWBA performance: such as pharmacokinetic evaluation of radiolabeled AS in blood and plasma, tissue/plasma partition coefficients, conversion pathway of AS to dihydroartemisinin (DHA, an active and major metabolite of AS), unchanged AS and DHA in plasma, mass balance assessment, urinary and faecal eliminations, drug pathway with conjugation, [14C] AS binding with RBC and plasma protein, and metabolites identification. Even though the each method has its own advantages, common profiles were obtained from the two processes as shown in the results of the biliary metabolism, long-lasting metabolites, tissue distribution profiles, and multiple concentration peaks, which indicate a [14C] AS enterohepatic circulation.