Work performed during the previous award of this grant tested the hypothesis that P-glycoprotein is the carrier for the renal secretion of organic cations. The experiments indicate that P-glycoprotein does not mediate classical renal organic cation secretion (OCT), i.e., refuting the hypothesis. OCT is characterized by organic cation/proton or organic cation/organic cation-exchange across the apical membrane of proximal tubule cells.
The aim of this application is to clone the cDNA and characterize the protein responsible for OCT. 2'-Deoxytubercidin (dTUB) is a selective substrate for OCT and it will be employed to identify the OCT carrier, as follows. Injection of total poly A+ mRNA into Xenopus oocytes enhances the oocytes' ability to efflux dTUB. The specific mRNA species responsible for the increased efflux will be cloned using this functional expression system. Once cloned and sequenced, biochemical features of the protein will be contrasted to those of other transport proteins. Transfection of the cDNA into MDCK cells (from dog kidney distal tubules) will allow us to study the physiological features of OCT in an epithelium that ordinarily lacks this transport function. The significance of this work is that the OCT has never been purified, hence its biochemical features are currently not known. Nonetheless, OCT is extremely important in that it serves to eliminate environmental and other toxins from our bodies via the kidney.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
2R01DK041606-04A1
Application #
2141827
Study Section
Special Emphasis Panel (ZRG3-ET-2 (03))
Project Start
1991-04-15
Project End
1999-03-31
Budget Start
1995-04-01
Budget End
1996-03-31
Support Year
4
Fiscal Year
1995
Total Cost
Indirect Cost
Name
University of Texas MD Anderson Cancer Center
Department
Pediatrics
Type
Other Domestic Higher Education
DUNS #
001910777
City
Houston
State
TX
Country
United States
Zip Code
77030
Pan, Bih Fang; Nelson, J Arly (2007) Dihydrodiol dehydrogenase in drug resistance and sensitivity of human carcinomas. Cancer Chemother Pharmacol 59:697-702
Chen, Rong; Jonker, Johan W; Nelson, J Arly (2002) Renal organic cation and nucleoside transport. Biochem Pharmacol 64:185-90
Chen, R; Nelson, J A (2000) Role of organic cation transporters in the renal secretion of nucleosides. Biochem Pharmacol 60:215-9
Chen, R; Pan, B F; Sakurai, M et al. (1999) A nucleoside-sensitive organic cation transporter in opossum kidney cells. Am J Physiol 276:F323-8
Pan, B F; Sweet, D H; Pritchard, J B et al. (1999) A transfected cell model for the renal toxin transporter, rOCT2. Toxicol Sci 47:181-6
Elfarra, A A; Duescher, R J; Hwang, I Y et al. (1995) Targeting 6-thioguanine to the kidney with S-(guanin-6-yl)-L-cysteine. J Pharmacol Exp Ther 274:1298-304
Nelson, J A; Dutt, A; Allen, L H et al. (1995) Functional expression of the renal organic cation transporter and P-glycoprotein in Xenopus laevis oocytes. Cancer Chemother Pharmacol 37:187-9
Pan, B F; Dutt, A; Nelson, J A (1994) Enhanced transepithelial flux of cimetidine by Madin-Darby canine kidney cells overexpressing human P-glycoprotein. J Pharmacol Exp Ther 270:1-7
Dutt, A; Heath, L A; Nelson, J A (1994) P-glycoprotein and organic cation secretion by the mammalian kidney. J Pharmacol Exp Ther 269:1254-60
Dutt, A; Priebe, T S; Teeter, L D et al. (1992) Postnatal development of organic cation transport and mdr gene expression in mouse kidney. J Pharmacol Exp Ther 261:1222-30