Klokouzas Antonios, Wu Chung-Pu, van Veen Hendrik W, Barrand Margery A, Hladky Stephen B
Department of Pharmacology, University of Cambridge, UK.
Eur J Biochem. 2003 Sep;270(18):3696-708. doi: 10.1046/j.1432-1033.2003.03753.x.
The nature of cGMP transport in human erythrocytes, its relationship to glutathione conjugate transport, and possible mediation by multidrug resistance-associated proteins (MRPs) have been investigated. MRP1, MRP4 and MRP5 are detected in immunoblotting studies with erythrocytes. MRP1 and MRP5 are also detected in multidrug resistant COR-L23/R and MOR/R cells but at greatly reduced levels in the parent, drug sensitive COR-L23/P cells. MRP4 is detected in MOR/R but not COR-L23/R cells. Uptake of cGMP into inside-out membrane vesicles prepared by a spontaneous, one-step vesiculation process is shown to be by a low affinity system that accounts for more than 80% of the transport at all concentrations above 3 micro m. This transport is reduced by MRP inhibitors and substrates including MK-571, methotrexate, estradiol 17-beta-d-glucuronide, and S(2,4-dinitrophenyl)glutathione (DNP-SG) and also by glibenclamide and frusemide but not by the monoclonal Ig QCRL-3 that inhibits high-affinity transport of DNP-SG by MRP1. It is concluded that the cGMP exporter is distinct from MRP1 and has properties similar to those reported for MRP4. Furthermore the evidence suggests that the protein responsible for cGMP transport is the same as that mediating low-affinity DNP-SG transport in human erythrocytes.
已对人红细胞中cGMP转运的性质、其与谷胱甘肽偶联物转运的关系以及多药耐药相关蛋白（MRP）可能的介导作用进行了研究。在对红细胞的免疫印迹研究中检测到了MRP1、MRP4和MRP5。在多药耐药的COR-L23/R和MOR/R细胞中也检测到了MRP1和MRP5，但在亲本的药物敏感COR-L23/P细胞中水平大幅降低。在MOR/R细胞中检测到了MRP4，但在COR-L23/R细胞中未检测到。通过自发的一步囊泡化过程制备的内翻膜囊泡对cGMP的摄取显示是通过一种低亲和力系统进行的，在所有浓度高于3μm时，该系统占转运的80%以上。MRP抑制剂和底物包括MK-571、甲氨蝶呤、雌二醇17-β-D-葡萄糖醛酸苷和S(2,4-二硝基苯基)谷胱甘肽（DNP-SG）以及格列本脲和呋塞米可降低这种转运，但抑制MRP1介导的DNP-SG高亲和力转运的单克隆Ig QCRL-3则不会。得出的结论是，cGMP转运体与MRP1不同，其性质与报道的MRP4相似。此外，证据表明负责cGMP转运的蛋白质与介导人红细胞中低亲和力DNP-SG转运的蛋白质相同。
