title: Characterization of [3H]Ro 5-4864 binding sites in rat vas deferens.
abstract: The presence of benzodiazepine binding sites in rat vas deferens was detected using [3H]Ro 5-4864 as a radioligand. The binding of [3H]Ro 5-4864 to the mitochondrial sites is saturable, reversible, and temperature and time dependent. The association rate constant (k1) was 8.7 +/- 0.7 x 10(7) M-1 min-1, and the dissociation rate constant (k-1) was 0.031 +/- 0.003 min-1. The dissociation constant (KD) determined by saturation binding was 5.22 +/- 0.56 nM. The density of binding was 4,926 +/- 565 fmol/mg of protein. The Hill coefficient of binding was 0.99 +/- 0.01, an indication that [3H]Ro 5-4864 binds to a single site. The [3H]Ro 5-4864 binding was inhibited competitively by Ro 5-4864 and 2-hydroxy-5-nitrobenzyl-6-thioguanosine and noncompetitively by PK 11195, nitrendipine, alpha,beta-methylene-ATP, and carboxyatractyloside and was not affected by clonazepam, dicyclohexylcarbodiimide, or protoporphyrin IX. Our data indicate that [3H]Ro 5-4864 binding sites are not identical to those labeled by PK 11195. These binding sites are modulated by the ADP/ATP mitochondrial carrier, and an interaction of dihydropyridines and [3H]Ro 5-4864 binding sites in rat vas deferens is suggested.
authors.affiliation: Laboratory of Pharmacology and Pharmacognosy, Faculty of Pharmacy, University of Barcelona, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Escubedo
authors.forename: A
authors.initials: A
authors.lastname: Camins
authors.forename: C
authors.initials: C
authors.lastname: Talaveron
authors.forename: J
authors.initials: J
authors.lastname: Camarasa
mesh_terms: D000818:Animals; D001570:Benzodiazepinones / Q000378:metabolism* / Q000493:pharmacokinetics; D001665:Binding Sites / Q000187:drug effects; D001667:Binding, Competitive; D006151:Guanosine / Q000031:analogs & derivatives / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D011963:Receptors, GABA-A / Q000378:metabolism; D013872:Thionucleosides / Q000378:metabolism; D013997:Time Factors; D014316:Tritium; D014649:Vas Deferens / Q000378:metabolism*
chemical_list: D001570:Benzodiazepinones; D007546:Isoquinolines; D011963:Receptors, GABA-A; D013872:Thionucleosides; D014316:Tritium; D006151:Guanosine; C028513:4'-chlorodiazepam; C003961:2-hydroxy-5-nitrobenzylthioguanosine; C037850:PK 11195