Inhibitor | [3H]Carnitine Uptake | |
---|---|---|
pmol/106 cells/30 min | % | |
Control | 1.21 ± 0.01 | 100 |
Organic cations | ||
TEA | 0.05 ± 0.01 | 4 |
MPTP | 0.05 ± 0.02 | 4 |
Choline | 0.29 ± 0.01 | 24 |
Cimetidine | 0.35 ± 0.05 | 29 |
Carnitine derivatives | ||
l-Carnitine | 0.04 ± 0.01 | 3 |
d-Carnitine | 0.12 ± 0.01 | 10 |
Acetyl-l-carnitine | 0.01 ± 0.01 | 1 |
Propionyl-l-carnitine | 0 | 0 |
Palmitoyl-dl-carnitine | 0 | 0 |
Betaine | 0.62 ± 0.02 | 51 |
HRPE cells were transfected with rOCTN2 cDNA, and expression was accomplished by the vaccinia virus expression system. Cells transfected with vector alone under similar conditions served for measurement of endogenous carnitine uptake in these cells. Only cDNA-specific carnitine uptake was used in data analysis. Uptake of [3H]carnitine (25 nM) was measured for 30 min in the presence of NaCl (pH 7.5). When present, the concentration of organic cations was 2 mM and that of carnitine, its acyl esters, and betaine was 0.5 mM. Values are means ± S.E.