TABLE 1

Effect of various deletion mutations of the putative intracellular loop of rat μ-opioid receptor on [3H]diprenorphine binding parameters

[3H]Diprenorphine saturation binding assays were carried out using membranes prepared from HEK 293 cells stably expressing wild-type or mutant receptors. For HEK 293 cells expressing 13-1. The saturation binding experiments were performed as described under Materials and Methods. Curve fitting for the binding data was performed using the GraphPad Prism program. Data represent mean ± S.E.M. of two (when Kd value was similar to wild-type to three (when Kd value was different from that of wild-type separate experiments in duplicate or triplicate.
Receptor
[3H]-Dipren Orphine Binding
Ko
Bmax
nM pmol/mg
WT 0.33 ± 0.01 9.4 ± 0.77
i3-1a 0.51 ± 0.08* 8.3 ± 0.32
i3-2 0.38 ± 0.03 10 ± 1.0
i3-3 0.39 ± 0.02 1.7 ± 0.04
i3-4 0.66 ± 0.11* 4.3 ± 1.6
i3-5 0.53 ± 0.05* 11 ± 0.39
5A
0.52 ± 0.06*
2.5 ± 0.01

  • WT, wild-type.

  • ↵ a The cells were pretreated with 10 μM naloxone for 48 h and then washed repeatedly to remove excess naloxone before membrane preparation.

  • ↵* Signifies p < 0.05 compared with control.