Gaganis Paraskevi, Miners John O, Brennan James S, Thomas Anthony, Knights Kathleen M
Department of Clinical Pharmacology, Flinders University, Adelaide, Australia.
J Pharmacol Exp Ther. 2007 Nov;323(2):422-30. doi: 10.1124/jpet.107.128603. Epub 2007 Aug 14.
There is currently little information regarding the localization of UDP-glucuronosyltransferases (UGTs) in human renal cortex and medulla, and the functional contribution of renal UGTs to drug glucuronidation remains poorly defined. Using human kidney sections and human kidney cortical microsomes (HKCM) and human kidney medullary microsomes (HKMM), we combined immunohistochemistry to investigate UGT1A and UGT2B7 expression with in vitro microsomal studies to determine the kinetics of S-naproxen acyl glucuronidation. With the exception of the glomerulus, Bowman's capsule, and renal vasculature, UGT1A proteins and UGT2B7 were expressed throughout the proximal and distal convoluted tubules, the loops of Henle, and the collecting ducts. Additionally, UGT1A and UGT2B7 expression was demonstrated in the macula densa, supporting a potential role of UGTs in regulating aldosterone. Consistent with the immunohistochemical data, S-naproxen acyl glucuronidation was catalyzed by HKCM and HKMM. Kinetic data were well described by the two-enzyme Michaelis-Menten equation. K(m) values for the high-affinity components were 34 +/- 14 microM (HKCM) and 45 +/- 14 microM (HKMM). Fluconazole inhibited the high-affinity component establishing UGT2B7 as the enzyme responsible for S-naproxen glucuronidation in cortex and medulla. The low-affinity component was relatively unaffected by fluconazole (<15% inhibition), supporting the presence of other UGTs with S-naproxen glucuronidation capacity (e.g., UGT1A6 and UGT1A9) in cortex and medulla. We postulate that the ubiquitous distribution of UGTs in mammalian kidney may buffer physiological responses to endogenous mediators, but at the same time competitive xenobiotic-endobiotic interactions may provide an explanation for the adverse renal effects of drugs, including nonsteroidal anti-inflammatory drugs.
目前，关于尿苷二磷酸葡萄糖醛酸转移酶（UGTs）在人肾皮质和髓质中的定位信息很少，而且肾脏UGTs对药物葡萄糖醛酸化的功能贡献仍不清楚。我们使用人肾切片、人肾皮质微粒体（HKCM）和人肾髓质微粒体（HKMM），结合免疫组织化学研究UGT1A和UGT2B7的表达，并通过体外微粒体研究来确定S-萘普生酰基葡萄糖醛酸化的动力学。除肾小球、鲍曼囊和肾血管外，UGT1A蛋白和UGT2B7在近端和远端曲小管、亨利襻和集合管中均有表达。此外，致密斑中也证实了UGT1A和UGT2B7的表达，这支持了UGTs在调节醛固酮方面的潜在作用。与免疫组织化学数据一致，HKCM和HKMM催化了S-萘普生酰基葡萄糖醛酸化。动力学数据可用双酶米氏方程很好地描述。高亲和力组分的K(m)值分别为34±14微摩尔/升（HKCM）和45±14微摩尔/升（HKMM）。氟康唑抑制了高亲和力组分，确定UGT2B7是皮质和髓质中负责S-萘普生葡萄糖醛酸化的酶。低亲和力组分相对不受氟康唑的影响（抑制率<15%），这支持了皮质和髓质中存在其他具有S-萘普生葡萄糖醛酸化能力的UGTs（如UGT1A6和UGT1A９）。我们推测，UGTs在哺乳动物肾脏中的普遍分布可能缓冲了对内源性介质的生理反应，但同时竞争性的外源性-内源性相互作用可能解释了药物（包括非甾体抗炎药）对肾脏的不良影响。
