Binding sites for a peripheral type benzodiazepine antagonist ([3H]PK 11195) in human iris.
Peripheral-type benzodiazepine binding sites have been characterized on sections of 8 normal human iris/ciliary-body preparations. Saturability was determined at 25 degrees C with [3H] PK 11195 (1 nM) a specific ligand of peripheral type sites. The studies revealed a single class of binding sites for PK 11195 with a nanomolar range affinity (KD = 1.45 nM) and a maximal capacity (Bmax) of 35.5 fmol/mg protein. The displacement potency order of the benzodiazepines tested suggest that these sites belong to the peripheral type: PK 11211 (IC50 = 12 nM) greater than Ro 5-4864 (IC50 = 770 nM) greater than clonazepam (IC50 = 20,000 nM). The present data demonstrate that high affinity binding sites for peripheral type benzodiazepines are present in human iris/ciliary-body. This tissue is therefore a suitable tool for evaluation of the putative functional role of these binding sites.
D000368:Aged; D001569:Benzodiazepines / Q000037:antagonists & inhibitors / Q000378:metabolism; D001667:Binding, Competitive; D002924:Ciliary Body / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007498:Iris / Q000378:metabolism*; D007546:Isoquinolines / Q000378:metabolism*; D007700:Kinetics; D011963:Receptors, GABA-A / Q000378:metabolism*
D007546:Isoquinolines; D011963:Receptors, GABA-A; D001569:Benzodiazepines; C037850:PK 11195