Table II.
Substrate/Inhibitor | hVMAT1a | hVMAT2a | rCGVMATb | bVMAT2c | Chromaffin Granulesd | |
---|---|---|---|---|---|---|
1 | 5HT | 1.4 ± 0.2 | 0.9 ± 0.1 | 0.85 ± 0.023 | 0.59 | 0.4 |
2 | DA | 3.8 ± 0.4 | 1.4 ± 0.2 | 1.56 ± 0.035 | 1.4 | - |
3 | NE | 13.7 ± 1.6 | 3.4 ± 0.5 | 2.5 ± 0.04 | 1.7 | 1.4 |
4 | E | 5.5 ± 0.7 | 1.9 ± 0.2 | 1.86 ± 0.011 | 2.5 | 1.4 |
5 | Tetrabenazine(TBZ) | >20 | 0.097 ± 0.002 | 0.027 | ||
6 | Reserpine (RES) | 0.034 ± 0.005 | 0.012 ± 0.003 | 0.0007 | ||
7 | Ketanserine (KET) | 1.7 ± 0.2 | 0.54 ± 0.07 | 0.170 | ||
9 | Histamine | 4500 ± 600 | 143 ± 12 | 436 ± 36 | - | |
10 | Phenylethylamine | 34 ± 5 | 3.7 ± 0.5 | |||
11 | Amphetamine (+) | 47 ± 6 | 2.1 ± 0.2 | |||
12 | Amphetamine (−) | 259 ± 33 | 10 ± 1.7 | |||
13 | MDMA (+/−) | 19 ± 3 | 6.9 ± 1.0 | |||
14 | Fenfluramine | 3.1 ± 0.4 | 5.1 ± 0.5 | |||
15 | MPP+ | 69 ± 10 | 8.9 ± 1.4 | 9.7 | 1.5 |
Determined using digitonin permiabilized CV-1 cells expressing c DNA of hVMAT1 and hVMAT2 in the presence of ATP. The apparent Km and Vmax parameters determined with [3H]5HT for VMAT1 and VMAT2 were 1.3 μM and 0.8 μM and 37 and 43 pmoles/min.450,000 cells, respectively. Inhibition of [3H]5HT uptake (90 nM) in the presence of various substrates were determined and Ki values were estimated by nonlinear regression analysis20.
Determined using the membranes prepared from the COS cells transfected with hCGVMAT in the presence of ATP. The apparent Km determined for [3H]5HT uptake was 0.3 μM. Inhibition of [3H]5HT uptake in the presence of various substrates were determined and Ki values were estimated by nonlinear regression analysis41.
Determined using homogenized COS cells expressing c DNA of bVMAT2 in the presence of ATP. The apparent Km and Vmax parameters were determined for [3H] norepinephrine were 1.9 μM and 32 pmoles/min.mg. The affinities of the substrates with respect to [3H] norepinephrine (IC50 values) were estimated by competitive experiments42.
Taken from the ref. 42.