Table 1.
Receptor affinities, selectivities and functional bioactivity of monomers 5 to 8 and bifunctional ligands 9 to 16.
| Receptor affinity (nM)a | Selectivity | Functional Bioactivityb | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Compounds | Ki δ | Ki μ |
Kiδ/ Kiμ |
Kiμ/ Kiδ |
MVD IC50 (nM) |
GTPγSc (pA2)δ |
GPI IC50 (nM) |
GTPγSc (pA2)μ |
|
| 5 | H-Dmt-Tic-OHd,e | 0.022e | 3.317e | 150e | 8.48d | ||||
| 6 | H-Dmt-Aba-Gly-NH-Bnf | 11 ± 2.3 | 0.46 ± 0.07 | 24 | 830 ± 70 | 51 ± 5 | |||
| 7 | H-Dmt-D-Aia-Gly-NH-Bnf | 160 ± 23 | 3.35 ± 0.28 | 48 | 1500 ± 139 | 14.9 ± 1.6 | |||
| 8 | Me2Dmt-Aia-Gly-OHf | 6.64 ± 0.89 | 874 ± 100 | 132 | 8.30 | ||||
|
| |||||||||
| 9 | ethylene-bis(H-Dmt-Tic-NH) | 0.96 ± 0.19 (4) | 10.20 ± 0.10(3) | 11 | >10000 | 9.04 ± 0.01 |
>10000 | 9.03 ± 0.13 |
|
| 10 | ethylene-bis(H-Dmt-Aba-Gly-NH) | 153.5 ± 8.6 (3) | 16.10 ± 1.2 (3) | 9.5 | >10000 | 7.74 ± 0.33 |
>10000 | 8.54 ± 0.47 |
|
| 11 | ethylene-bis(H-Dmt-D-Aia-Gly-NH) | 211.0 ± 13 (3) | 138.7 ± 41 (3) | 1.5 | NT | NA | NT | NA | |
| 12 | ethylene-bis(Me2Dmt-Aia-Gly-NH) | 101.2 ± 6.4 (3) | 343.5 ± 32 (3) | 3.4 | NT | NA | NT | NA | |
| 13 | (p-xylylene)bis(H-Dmt-D-Aia-Gly-NH) | 360.6 ± 33 (3) | 176.9 ± 22 (3) | 2 | NT | NA | NT | NA | |
| 14 | 1,6-(hex-3-ene)bis(H-Dmt-Tic-NH) | 0.24 ± 0.04 (4) | 1.50 ± 0.07 (3) | 6.3 | >10000 | 8.94 ± 0.08 |
>10000 | 8.31 ± 0.38 |
|
| 15 | tris-[H-Dmt-Tic-NH-ethylene]-N | 3.75 ± 0.81 (4) | 7.78 ± 0.63 (3) | 2.1 | >10000 | 8.64 ± 0.63 |
>10000 | 7.48 ± 0.11 |
|
| 16 | tris-[H-Dmt-Aba-Gly-NH-ethylene]-N | 196.1 ± 13 (3) | 8.06 ± 0.83 (4) | 24 | >10000 | 7.64 ± 0.54 |
>10000 | 6.95 ± 0.21 |
|
The Ki values (nM) were determined according to Cheng and Prusoff,29 using published methods.30 Radioligands were [3H]DAMGO (Perkin-Elmer) for μ-opioid receptors and [3H]deltorphin II (NEN) for δ, and affinity determined using the P2 preparation of rat brain membranes. The mean ± SEM values of three to six repetitions are based on independent binding assays conducted in duplicate using five to eight grade doses of peptides with different synaptosomal preparations.
Agonism was expressed as IC50 obtained from dose response curves.31 These values represent the mean ± SEM of at least six fresh tissue samples. Deltorphin C and dermorphin were the internal standards for MVD (δ-opioid receptor bioactivity) and GPI (μ-opioid receptor bioactivity) tissue preparations, respectively.
Effect of compounds 10 to 16 on loperamide and deltorphin C stimulated GTPγS binding in SK-N-SH and NG108-15 cell membranes, respectively. NA: not active (>20.000nM); NT: not tested.
Values taken from ref. 23
Values taken from ref. 32
Values taken from ref. 22.