Transport of choline and its relationship to the expression of the organic cation transporters in a rat brain microvessel endothelial cell line (RBE4)
| Autor: | Anne Friedrich, Ronald L. George, Vadivel Ganapathy, Christy C. Bridges, Puttur D. Prasad |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
1-Methyl-4-phenylpyridinium
Transcription Genetic Biophysics Choline uptake Kidney Biochemistry Clonidine Cell Line Choline Blood–brain barrier chemistry.chemical_compound Hemicholinium-3 Animals RNA Messenger Tetramethylammonium Organic cation transport proteins Tetraethylammonium biology Reverse Transcriptase Polymerase Chain Reaction Organic cation transporter Microcirculation Sodium Organic Cation Transporter 1 Brain Membrane Proteins Transporter Biological Transport Cell Biology Hemicholinium 3 Rats Choline transporter Endothelial stem cell Quaternary Ammonium Compounds Kinetics chemistry 1-Methyl-4-phenyl-1 2 3 6-tetrahydropyridine Cerebrovascular Circulation biology.protein Rat Endothelium Vascular Carrier Proteins Brain Stem |
| Zdroj: | Biochimica et biophysica acta. 1512(2) |
| ISSN: | 0006-3002 |
| Popis: | The present study was undertaken to elucidate the functional characteristics of choline uptake and deduce the relationship between choline uptake and the expression of organic cation transporters in the rat brain microvessel endothelial cell line RBE4. Confluent RBE4 cells were found to express a high affinity choline uptake system. The system is Na(+)-independent and shows a Michaelis-Menten constant of approx. 20 microM for choline. The choline analogue hemicholinium-3 inhibits choline uptake in these cells with an inhibition constant of approx. 50 microM. The uptake system is also susceptible for inhibition by various organic cations, including 1-methyl-4-phenylpyridinium, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, clonidine, procainamide, and tetramethylammonium. The prototypical organic cation tetraethylammonium shows very little affinity for the choline uptake system in these cells. The inhibition of choline uptake by hemicholinium-3 is competitive. Northern analysis and RT-PCR show that these cells do not express the organic cation transporters OCT2 and OCT3. These cells do express, however, low levels of OCT1, but the functional characteristics of choline uptake in these cells are very different from the known properties of choline uptake via OCT1. The Na(+)-coupled high affinity choline transporter CHT1 is not expressed in these cells as evidenced by RT-PCR. This corroborates the Na(+)-independent nature of choline uptake in these cells. It is concluded that RBE4 cells express an organic cation transporter that is responsible for choline uptake in these cells and that this transporter is not identical to any of the organic cation transporters thus far identified at the molecular level in mammalian cells. |
| Databáze: | OpenAIRE |
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