Peripheral-type benzodiazepine receptors are highly concentrated in mitochondrial membranes of rat testicular interstitial cells.
The binding of 3H-RO 5-4864 to the peripheral-type benzodiazepine receptors (PBZDR) in rat testicular interstitial cells (TIC) was characterized. The binding was saturable, reversible and showed a single high-affinity (Kd = 5.02 +/- 0.86 nM) class of binding sites. The maximal binding capacity (Bmax) in crude mitochondrial fractions (77.6 +/- 9.1 pmol/mg protein) represents the highest density of PBZDR in tissues thus far studied. In comparison with the crude mitochondrial fraction the subcellular fractionation of TIC revealed a 2-fold enrichment of 3H-RO 5-4864 binding sites to the purified mitochondria (Bmax = 140 +/- 23 pmol/mg protein). The ability of various drugs to displace 3H-RO 5-4864 from TIC binding sites was examined and the inhibition constants (Ki) for RO 5-4864, PK 11195, diazepam and flunitrazepam were 3.5, 4.4, 159, and 353 nM, respectively, whereas clonazepam and RO 15-1788 were inefficient in displacing 3H-RO 5-4864 (Ki greater than 10 microM). This pharmacological profile is characteristic of PBZDR described in other tissues. In conclusion, rat TIC possess a very high concentration of PBZDR primarily associated with mitochondrial membranes.
Calvo
D J
DJ
Instituto de Biologia Celular, Facultad de Medicina UBA, Argentina.
Ritta
M N
MN
Calandra
R S
RS
Medina
J H
JH
D000818:Animals; D001570:Benzodiazepinones / Q000378:metabolism; D001667:Binding, Competitive; D003975:Diazepam / Q000378:metabolism; D005445:Flunitrazepam / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D007546:Isoquinolines / Q000378:metabolism; D007700:Kinetics; D007985:Leydig Cells / Q000648:ultrastructure*; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011963:Receptors, GABA-A / Q000378:metabolism*
D001570:Benzodiazepinones; D007546:Isoquinolines; D011963:Receptors, GABA-A; C028513:4'-chlorodiazepam; D005445:Flunitrazepam; D003975:Diazepam; C037850:PK 11195