de Loor Henriette, Naesens Maarten, Verbeke Kristin, Vanrenterghem Yves, Kuypers Dirk R
Department of Nephrology and Renal Transplantation, University Hospitals Leuven, Leuven, Belgium.
Clin Chim Acta. 2008 Mar;389(1-2):87-92. doi: 10.1016/j.cca.2007.11.033. Epub 2007 Dec 7.
In recent years there is growing interest in therapeutic drug monitoring of mycophenolic acid (MPA) and its glucuronide metabolites MPAG and AcMPAG. Like other acyl glucuronide metabolites, AcMPAG has a limited stability, but this aspect has received little attention.
Plasma sample deproteinization with perchloric acid 2 M (method A) was compared to metaphosphoric acid 15% (method B). Stability of MPA, MPAG and AcMPAG in acidified and non-acidified plasma stored at room temperature, 4 degrees C, -20 degrees C and -80 degrees C was assessed over short and long time intervals using HPLC-UV methodology.
The area ratio of AcMPAG/IS on spiked plasma at pH 2.5 with method A was 63% of the respective ratio in water, in contrast to 102% with method B, suggesting partial deconjugation and/or incomplete release of AcMPAG from proteins with method A. At room temperature, AcMPAG concentrations in both whole blood and non-acidified plasma decreased significantly after 2-5 h. MPA, MPAG and AcMPAG concentrations remained stable in acidified plasma stored at -20 degrees C and -80 degrees C, but not longer than 5 months after collection.
It is concluded that adequate sample collection, storage measures and deproteinization methods should be applied in order to avoid deconjugation and hence underestimation of MPA, MPAG and AcMPAG concentrations.
近年来，人们对霉酚酸（MPA）及其葡萄糖醛酸代谢产物MPAG和AcMPAG的治疗药物监测越来越感兴趣。与其他酰基葡萄糖醛酸代谢产物一样，AcMPAG的稳定性有限，但这方面很少受到关注。
将用2 M高氯酸进行血浆样品脱蛋白处理（方法A）与用15%偏磷酸进行处理（方法B）进行比较。使用高效液相色谱 - 紫外检测方法，在短时间和长时间间隔内，评估MPA、MPAG和AcMPAG在室温、4℃、-20℃和-80℃下储存的酸化和非酸化血浆中的稳定性。
采用方法A时，加标血浆在pH 2.5条件下AcMPAG/内标物的面积比是水中相应比例的63%，而采用方法B时为102%，这表明方法A会导致AcMPAG从蛋白质中部分去结合和/或释放不完全。在室温下，全血和非酸化血浆中的AcMPAG浓度在2 - 5小时后显著下降。MPA、MPAG和AcMPAG浓度在-20℃和-80℃储存的酸化血浆中保持稳定，但采集后不超过5个月。
得出的结论是，应采用适当的样品采集、储存措施和脱蛋白方法，以避免去结合，从而避免低估MPA、MPAG和AcMPAG的浓度。
