Kinetic parameters of Bamet-R2 and Bamet-UD2 uptake by X. laevis oocytes injected with the cRNA of human NTCP, OATP-A, OATP-C, OCT1, or OCT2
| Bamet-R2 | Bamet-UD2 | |||||
|---|---|---|---|---|---|---|
| Km | Vmax | Et | Km | Vmax | Et | |
| μM | pmol/oocyte/10 min | nl/oocyte/10 min | μM | pmol/oocyte/10 min | nl/oocyte/10 min | |
| NTCP | 27.0 ± 8.9 | 2.6 ± 0.3 | 96 | 33.2 ± 8.5 | 3.3 ± 0.3 | 99 |
| OATP-A | 23.8 ± 8.1 | 3.5 ± 0.4 | 147 | 14.1 ± 2.4 | 3.7 ± 0.2 | 262 |
| OATP-C | 10.0 ± 1.5 | 4.5 ± 0.2 | 450 | 9.7 ± 2.0 | 5.5 ± 0.3 | 567 |
| OCT1 | 57.7 ± 12.0 | 2.8 ± 0.3 | 48 | 15.4 ± 5.6 | 2.5 ± 0.3 | 162 |
| OCT2 | 13.1 ± 2.3 | 4.1 ± 0.2 | 313 | 8.0 ± 2.4 | 4.4 ± 0.3 | 550 |
Apparent K m andV max values were obtained by fitting the results of drug uptake by X. laevis oocytes incubated at varying drug concentrations (from 0 to 100 μM). Efficiency of transport (Et) was calculated fromV max/K m. Two days before carrying out uptake studies, the oocytes were injected with TE buffer, either alone or containing 7 ng of cRNA of human NTCP, OATP-A, OATP-C, OCT1, or OCT2. Between 10 and 20 oocytes were used to calculate mean values at each substrate concentration by subtracting the uptake observed in oocytes injected with TE buffer alone from that found in oocytes injected with the cRNA of the carrier. Values are means ± S.D.