During drug development, detailed investigations of the pharmacokinetic profile of the drug are required to characterize its absorption, distribution, metabolism, and excretion properties. Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) is an established technique for studies of the distribution of drugs and their metabolites. It has advantages over autoradiography, which is conventionally used for distribution studies: it does not require the radiolabeling of drugs and can distinguish between the drug and its metabolites directly in the tissue. However, its lack of sensitivity in certain cases remains challenging. Novel procedures, such as on-tissue chemical derivatization (OTCD), could be developed to increase sensitivity. We used OTCD to enhance the sensitivity of MALDI-MSI for one of the most widely used drugs, acetaminophen, and to study its distribution in tissues. Without derivatization, this drug and some of its metabolites are undetectable by MALDI-MSI in the tissues of treated rats. We used 2-fluoro-1-methylpyridinium p-toluene sulfonate as a derivatization reagent, to increase the ionization yield of acetaminophen and some of its metabolites. The OTCD protocol made it possible to study the distribution of acetaminophen and its metabolites in whole-body sections at a spatial resolution of 400 μm and in complex anatomical structures, such as the testis and epididymis, at a spatial resolution <50 μm. The OTCD is also shown to be compatible with the quantification of acetaminophen by MALDI-MSI in whole-body tissues. This protocol could be applied to other molecules bearing phenol groups and presenting a low ionization efficiency.

中文翻译：

---

通过组织化学衍生化后的基质辅助激光解吸/电离质谱成像研究对乙酰氨基酚及其代谢物在大鼠体内的分布，从全身到离体器官水平

在药物开发过程中，需要详细研究药物的药代动力学特征，以表征其吸收、分布、代谢和排泄特性。基质辅助激光解吸/电离 (MALDI) 质谱成像 (MSI) 是研究药物及其代谢物分布的成熟技术。与通常用于分布研究的放射自显影相比，它具有优势：它不需要对药物进行放射性标记，并且可以直接在组织中区分药物及其代谢物。然而，它在某些情况下缺乏敏感性仍然具有挑战性。可以开发新的程序，例如组织上化学衍生化 (OTCD)，以提高灵敏度。我们使用 OTCD 来提高 MALDI-MSI 对最广泛使用的药物之一对乙酰氨基酚的敏感性，并研究其在组织中的分布。未经衍生化处理，MALDI-MSI 在治疗大鼠的组织中无法检测到该药物及其某些代谢物。我们使用了 2-fluoro-1-methylpyridinium对甲苯磺酸盐作为衍生试剂，以提高对乙酰氨基酚及其部分代谢物的电离产率。OTCD 协议使研究对乙酰氨基酚及其代谢物在全身切片中的分布成为可能，空间分辨率为 400 μm，复杂解剖结构（如睾丸和附睾）中的分布可以<50 μm。OTCD 也被证明与 MALDI-MSI 在全身组织中对乙酰氨基酚的量化兼容。该协议可应用于其他带有苯酚基团并呈现低电离效率的分子。