Using epifluorescence microscopy I have characterized the transport of the fluorescent organic cation NBD-TMA⁺, [2-(4-nitro-2,1,3-benzoxadiaxol-7-yl)aminoethyl]trimethylammonium. NBD-TMA⁺ has structural characteristics common to other secreted organic cations and it is fluorescent (λₑₓ = 458 nm; λ(em) = 530 nm). Transport of NBD-TMA⁺ by rabbit renal proximal tubules was time dependent, saturable, and inhibited by TEA⁺, cimetidine, and procainamide. These results provide strong evidence that the fluorescent organic cation, NBD-TMA⁺, is transported by the classical organic cation transporter and can be used to monitor organic cation transport in renal proximal tubules or cells expressing organic cation transporters. Additionally, a stable line of HeLa cells expressing hOCT1 was used to investigate the structural and chemical characteristics influencing substrate binding to the transporter. I found that the systematic rotation of a planar hydrophobic mass about a vertical axis aligned with the positively charged nitrogen reduced the binding affinity of substrate for hOCT1 suggesting that hOCT1 possesses a lateral steric limitation not seen in the apical organic cation transporter. Furthermore, the addition of supraplanar hydrophobic mass to a planar chemical structure was found to increase the binding affinity for a substrate substantially more that expected for the increased hydrophobicity suggesting that the binding site for hOCT1 is not simply planar in nature, but may be better described as a pocket.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/290546 |
| Date | January 2001 |
| Creators | Bednarczyk, Dallas Joesph |
| Contributors | Wright, Stephen H. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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