| Co-Investigator(Kenkyū-buntansha) |
OSANAI Arihiro Hirosaki University, School of Medicine, Instructor, 医学部, 助手 (30361009)
KAMIYA Haruo Hirosaki University, School of Medicine, Professor, 医学部, 教授 (70002079)
FURUOKA Hidefumi Obihiro University of Agriculture and Veterinary Medicine, School of Veterinary Medicine, Associate professor, 畜産学部, 助教授 (60238665)
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| Budget Amount *help |
¥6,400,000 (Direct Cost: ¥6,400,000)
Fiscal Year 2004: ¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2003: ¥3,500,000 (Direct Cost: ¥3,500,000)
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| Research Abstract |
Excretion of metabolic wastes as well as xenobiotics is a major concern of all living organisms, and the Platyhelminthes including Schistosoma mansoni possess the protonephridial excretory system for their survival. To assess the excreoty activity of S.mansoni, we established a new technique using the fluorescent marker resorufin, which is a potential substrate of the drug efflux pump, P-glycoprotein (P-gp). After simple diffusion into the schistosome body, fluorescent resorufin was concentrated in the excretory tubules by an energy-dependent mechanism and excreted via the nephridiopore. The present technique of labeling functionally the excreotry system was applicable to adult worms, but not schistosomula or cercariae. A variety of modulators known to interfere with mammalian P-gp function perturbed resorufin excretion from schistosomes. Then, to determine the presence of the multidrug resistance-associated protein (MRP) as a possible transporter in protonephridial epithelium, adult s
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chistosomes were exposed to fluorescent substrates such as fluo-3 AE, monoclorobimane, fluoresce in diacetate, and 5(6)-carboxy-fluorescein diacetate, which are potential substrates of mammalian MRP. Similarly as in P-gp experiments, fluorescent MRP substrates were accumulated in the excretory tubules of adult schistosomes, but not schistosomula or cercariae. These findings suggest that the protonephridial epithelium of adult schistosomes, but not schistosomula, might express the homologues of the mammalian P-gp and MRP. The study was extended to a cestode, Echinococcus multilocularis, and a protozoon, Trypanosoma grosi. The fluorescent marker accumulated in the excretory tubules of the larva (protoscolex) of E.multiilocularis, but not of its adults. Molecular biological characterization of the parasite homologues of mammalian P-gp and MRP is in progress. Our approaches are important to understand the physiological function, hitherto unknown, of the protonephridial system of parasitic platyhelminthes. Less
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