TABLE 1.
Kinetic Parameters For Net Transport of Hg2+-Thiol Conjugates Across Isolated Basolateral Plasma Membrane (BLM) Vesicles from Kidneys of Control and NPX Rats
| Control
|
NPX
|
|||
|---|---|---|---|---|
| Vmax | Km | Vmax | Km | |
| Hg-(GSH)2 | ||||
| −Na+ | ||||
| System 1 | 3.50 ± 0.22 | 4.47 ± 0.25 | 3.85 ± 0.19 | 3.43 ± 0.24 |
| System 2 | 9.27 ± 0.61 | 29.6 ± 1.7 | 11.5 ± 0.8 | 28.6 ± 1.5 |
| Na+-dependent | ||||
| System 1 | 3.34 ± 0.20 | 8.82 ± 0.43 | 4.36 ± 0.18 | 1.98 ± 0.08 |
| System 2 | 12.2 ± 0.5 | 85.9 ± 2.7 | 15.5 ± 0.7 | 41.6 ± 1.9 |
| Hg-(Cys)2 | ||||
| −Na+ | ||||
| System 1 | 7.42 ± 0.32 | 1.08 ± 0.07 | 11.1 ± 0.7 | 1.72 ± 0.06 |
| System 2 | 21.6 ± 1.3 | 22.2 ± 1.0 | 24.8 ± 1.1 | 15.4 ± 0.6 |
| Na+-dependent | ||||
| System 1 | 7.47 ± 0.95 | 3.26 ± 0.29 | 8.07 ± 0.66 | 0.88 ± 0.12 |
| System 2 | – | – | 13.7 ± 1.1 | 9.11 ± 0.75 |
| Hg-(NAcCys)2 | ||||
| −Na+ | ||||
| System 1 | 3.00 ± 0.28 | 0.60 ± 0.05 | 3.73 ± 0.23 | 2.30 ± 0.11 |
| System 2 | 21.0 ± 2.2 | 59.8 ± 4.8 | 19.5 ± 0.6 | 56.4 ± 1.8 |
| Na+-dependent | ||||
| System 1 | 2.32 ± 0.13 | 1.50 ± 0.06 | 5.54 ± 0.76 | 1.40 ± 1.5 |
| System 2 | 8.96 ± 0.35 | 34.4 ± 2.1 | 7.36 ± 0.62 | 5.79 ± 0.44 |
Note. Eadie-Hofstee plots of net Hg2+ accumulation data (−Na+ and Na+-dependent uptake) were derived from data presented in Figure 4 for Hg-(GSH)2, Hg-(Cys)2, and Hg-(NAcCys)2 and are shown in Figures 5–7. In all cases but one, Eadie-Hofstee plots could discriminate between two carrier-mediated processes. Results are derived from experiments with membrane vesicles from three control or three NPX rat kidneys. Vmax values are expressed as nmol/30 s per milligram of protein, and Km values are expressed as μM Hg2+-thiol.