Table 1

Densities of recombinant receptors and agonist-activated G proteins in CHO cells stably expressing hD2 and hD3 receptors

Cell LineCHO-hD3CHO-hD3 (EEDQ)CHO-hD2
Receptor Saturation
B max(pmol/mg)15.43  ± 1.337.36  ± 1.171.39  ± 0.19
K D (nM)1.18  ± 0.191.31  ± 0.030.48  ± 0.05
G Protein Saturation
B max (pmol/mg)3.38  ± 0.512.58  ± 0.530.92  ± 0.05
K APP(nM)6.72  ± 1.296.18  ± 1.081.68  ± 0.30
R/GB maxRatio4.62.91.5

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.