Binding of [³H]Ro 5–4864 and [³H]PK 11195 to Cerebral Cortex and Peripheral Tissues of Various Species: Species Differences and Heterogeneity in Peripheral Benzodiazepine Binding Sites

Abstract

The binding of [3H]PK 11195 and [3H]Ro 5-4864 to membrane preparations from cerebral cortex and peripheral tissues of various species was studied. [3H]PK 11195 (0.05-10 nM) bound with high affinity to rat and calf cerebral cortical and kidney membranes. [3H]Ro 5-4864 (0.05-30 nM) also successfully labeled rat cerebral cortical and kidney membranes, but in calf cerebral cortical and kidney membranes, its binding capacity was only 3 and 4%, respectively, of that of [3H]PK 11195. Displacement studies showed that unlabeled Ro 5-4864, diazepam, and flunitrazepam were much more potent in displacing [3H]PK 11195 from rat cerebral cortex and kidney membranes than from calf tissues. The potency of unlabeled Ro 5-4864 in displacing [3H]PK 11195 from the cerebral cortex of various other species was also tested, and the rank order of potency was rat = guinea pig greater than cat = dog greater than rabbit greater than calf. Analysis of these displacement curves revealed that Ro 5-4864 bound to two populations of binding sites from rat and calf kidney and from rat, guinea pig, rabbit, and calf cerebral cortex but to a single population of binding sites from cat and dog cerebral cortex. Using [3H]PK 11195 as a ligand, the rank order of binding capacity in cerebral cortex of various species was cat greater than calf greater than guinea pig greater than rabbit greater than dog greater than rat, whereas when [3H]Ro 5-4864 was used, the rank order of binding capacity was cat greater than guinea pig greater than rat greater than rabbit greater than calf greater than dog.

The 18 kDa Translocator Protein as a Potential Participant in Atherosclerosis

“…I n c o n t r a s t t o a o r t a , a h i g h l y significant enhancement in the B max o f T S P O ( + 4 1 % ) determined with [ 3 H]PK 11195 binding was observed in testis tissue due to the HFHC + DMBA treatment, compared to control (data not shown). This was similar to the effects seen with HFHC diet alone and DMBA treatment alone (Dimitrova-Shumkovska et al, 2010a,b,c (Awad & Gavish, 1987;Dimitrova-Shumkovska et al, 2010a,b). This implies also that all of these K d values were not affected by HFHC and DMBA exposure.…”

“…PK 11195 and Ro5-4864 compete with each other in binding experiments, suggesting overlapping but not necessarily identical binding sites. It has been suggested that they interact with two different conformations or domains of the mitochondrial TSPO (Awad & Gavish, 1987). Behavioral studies have demonstrated that Ro5-4864 possesses anxiogenic and convulsant properties, whereas PK 11195 has been found to be anxiolytic and anticonvulsant (Gavish et al, 1999).…”

“…Widely expressed throughout the body, TSPO exhibit different patterns of tissue specific expression (Golani et al, 2001;Veenman et al, 2002). In vivo studies showed the rank order of TSPO binding density in rats to be adrenal >> kidney ~ heart ~ testis ~ ovary >> liver ~ brain (Awad & Gavish, 1987;Gavish et al, 1999). In humans and dogs, the heart appears to be one of the organs with high TSPO density (Veenman & Gavish, 2006).…”

Effects of Peripheral-type Benzodiazepine Receptor Antisense Knockout on MA-10 Leydig Cell Proliferation and Steroidogenesis

“…Control and 18-kDa PBR mRNA knockout cells were dubbed EnKat and anti-18-kDa PBR cells, respectively. 5 Ci/mmol; NEN Life Science Products) were used for binding studies, as described previously (25). Cells were scraped from 90-mm 2 culture dishes, washed with phosphate-buffered saline, and centrifuged at 1200 ϫ g for 5 min.…”

Decreases in Binding Capacity of the Mitochondrial 18 kDa Translocator Protein Accompany Oxidative Stress and Pathological Signs in Rat Liver After DMBA Exposure

“…Maximal binding capacity (B max ) and equilibrium dissociation constant (K d ) of the binding of the TSPO-specific ligand [ 3 H]PK 11195 were determined in whole cell membrane homogenates from the liver, as previously described (Awad and Gavish 1987). Radioactivity was counted with a 1600CA Tri-Carb liquid scintillation analyzer (Packard, Meriden, CT, USA).…”