The affinities of L-745,870, L-750,667, and NGD 94-1 for the D2-V2.61(91)F mutant receptor are significantly enhanced in the presence of 140 mM NaCl Receptors were stably expressed in the HEK293 cell line. Binding affinities (Ki) were calculated from the Cheng-Prusoff equation, Ki = IC50/(1+[radioligand]/KD, and expressed as geometric mean values (nanomolar) ± S.E.M. (n = 3). The D2-V2.61(91)F was run in three paired experiments, whereas wild-type D2 was run only in two paired experiments.
D2-WT* | D2-V2.61(91)F | |||||
|---|---|---|---|---|---|---|
| No NaCl | 140 mM NaCl | No NaCl | 140 mM NaCl | |||
| L-745,870 | 5232 ± 8419 (1) | 778 ± 89 (↓7) | 943 ± 328* (1) | 27.0 ± 4.34 (↓35) | ||
| L-750,667 | >10,000 (1) | 1331 ± 927 (>↓7) | 1271 ± 924* (1) | 34 ± 24 (↓37) | ||
| NGD 94-1 | >10,000 (1) | 3827 ± 3299 (>↓3) | >10,000* (1) | 616 ± 128* (>↓16) | ||
↵* These are approximate values based upon extrapolation. The fold changes in affinity values relative to the receptor in the absence of sodium are shown in parentheses with the direction of the change indicated by arrows: ↓, decrease in Ki value corresponding to an increased affinity