Binding affinities of peptides to the GnRH and endothelin receptors
| Peptide | Sequence | Ki | |
|---|---|---|---|
| GnRH Receptor | ET Receptor | ||
| μM | |||
| ET-1 | NB | 0.002 | |
| ET[16–21] | His-Leu-Asp-Ile-Ile-Trp-OH | NB | NB |
| Peptide 1 | Ac-D-Trp-Leu-Asp-Ile-Ile-Trp-OH | 1.9 ± 0.5 | 0.12 ± 0.07 |
| Peptide 2 | D-Trp-Leu-Asp-Ile-Ile-Trp-OH | 8 ± 1 | 55 ± 15 |
| GnRH | pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2 | 0.002 | NB |
K i is the inhibition constant for the displacement of specific binding of 125I-[d-Lys6]GnRH (K d = 177 pM) or of 125I-ET-1 (K d = 2 nM) bound to rat pituitary membranes. Values are based on displacement curves obtained by incubating pituitary membranes for 90 min at 4°C with the respective tracer and increasing concentrations of the unlabeled peptides, as described inExperimental Procedures. Nonspecific binding was determined in the presence of 1 μM of GnRH or of ET-1 and subtracted from the total binding for the calculation of specific binding. Results are mean ± S.E. of two experiments carried out in triplicate.
NB, no significant binding at 10 μM; pGlu, pyroglutamic acid.