Densities of recombinant receptors and agonist-activated G proteins in CHO cells stably expressing hD2 and hD3 receptors
| Cell Line | CHO-hD3 | CHO-hD3 (EEDQ) | CHO-hD2 |
|---|---|---|---|
| Receptor Saturation | |||
| B max(pmol/mg) | 15.43 ± 1.33 | 7.36 ± 1.17 | 1.39 ± 0.19 |
| K D (nM) | 1.18 ± 0.19 | 1.31 ± 0.03 | 0.48 ± 0.05 |
| G Protein Saturation | |||
| B max (pmol/mg) | 3.38 ± 0.51 | 2.58 ± 0.53 | 0.92 ± 0.05 |
| K APP(nM) | 6.72 ± 1.29 | 6.18 ± 1.08 | 1.68 ± 0.30 |
| R/GB maxRatio | 4.6 | 2.9 | 1.5 |
Receptor expression levels (Bmax) of hD3 and hD2 receptors stably expressed in CHO cell membranes were determined by saturation binding experiments with [125I]iodosulpride. Treatment of CHO-hD3 membranes with EEDQ (33 μM) significantly reduced hD3 receptor expression (p < 0.05, 2-tailed t test). Number of dopamine-activated G proteins was determined by [35S]GTPγS isotopic dilution saturation binding, as described in Materials and Methods. ApparentKD for [35S]GTPγS saturation binding is denoted KAPP. EEDQ (33 μM) treatment of CHO-hD3 membranes did not significantly alterBmax or KAPP for [35S]GTPγS saturation.
Data are means ± S.E.M. of at least three independent determinations.