Affinities of polyamines and polyamine antagonists for [3H]ifenprodil binding to human retinal homogenates
| Compound | Apparent affinity in human retina (Ki; μM) |
Pseudo-Hill coefficient (nH) |
|---|---|---|
| Ifenprodil | 0.7 (0.1) | 0.6 (0.1)* |
| Eliprodil | 6.8 (0.7) | 1.0 (0.1) |
| Arcaine | 20.2 (4.7) | 0.8 (0.1) |
| Spermine | 27.6 (2.6) | 1.0 (0.1) |
| Diaminodecane | 51.2 (15.3) | 0.8 (0.2) |
| Spermidine | 81.2 (15.9) | 0.8 (0.1) |
| Putrescine | >560 | — |
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Data are mean (SEM) from 3–7 independent experiments. [3H]ifenprodil binding was conducted in the presence of 3 μM DTG and 10 μM GBR12909 to block sigma binding sites. *nH significantly <1, and dissection of the biphasic competition curves yielded the data presented in the Results section. Preliminary studies with rat and rabbit retinas yielded the following estimated affinities: ifenprodil = 0.5–0.9 μM, eliprodil = 0.9–1.1 μM, spermine = 47–67 μM, spermidine = >100 μM and putrescine = >650 μM.
