Endogenous [3H]flunitrazepam binding in human embryonic kidney cell line 293.
Specific endogenous [3H]flunitrazepam binding sites were identified and characterized in membranes from the human embryonic kidney (HEK) cell line 293. A large part of these binding sites exhibited an intermediate affinity for [3H]flunitrazepam and a microM affinity for diazepam, clonazepam, 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxam ide (PK 11195) or 4'-chlorodiazepam (Ro 5-4864). These sites, thus, resembled neither gamma-aminobutyric acidA (GABAA) receptor associated nor 'peripheral' benzodiazepine binding sites. A small part of the binding sites labeled by [3H]flunitrazepam seemed to belong to 'peripheral' benzodiazepine binding sites exhibiting a nM affinity for PK 11195, and another small part of the binding sites seemed to exhibit a high affinity for flunitrazepam and PK 11195. Although small amounts of mRNA for alpha 1-, beta 3- and gamma 2-subunits of GABAA receptors could be identified in HEK 293 cells, neither the actual expression of GABAA receptors in these cells nor a coassembly of endogenous subunits with transfected GABAA receptor subunits could be demonstrated by binding studies.
Fuchs
K
K
Department of Biochemical Psychiatry, University Clinic for Psychiatry, Vienna, Austria.
Zezula
J
J
Slany
A
A
Sieghart
W
W
D001483:Base Sequence; D002460:Cell Line; D004622:Embryo, Mammalian / Q000378:metabolism; D005445:Flunitrazepam / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000196:embryology / Q000378:metabolism*; D008969:Molecular Sequence Data; D011869:Radioligand Assay; D011963:Receptors, GABA-A / Q000378:metabolism*
D011963:Receptors, GABA-A; C079942:flunitrazepam receptor; D005445:Flunitrazepam