Table 1

Affinities of polyamines and polyamine antagonists for [3H]ifenprodil binding to human retinal homogenates

CompoundApparent affinity in human retina
(Ki; μM)
Pseudo-Hill coefficient (nH)
Ifenprodil0.7 (0.1)0.6 (0.1)*
Eliprodil6.8 (0.7)1.0 (0.1)
Arcaine20.2 (4.7)0.8 (0.1)
Spermine27.6 (2.6)1.0 (0.1)
Diaminodecane51.2 (15.3)0.8 (0.2)
Spermidine81.2 (15.9)0.8 (0.1)
Putrescine>560
  • 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.