Characterization of nitrobenzylthioinosine binding sites in the mitochondrial fraction of rat testis.
The presence of [3H] NBMPR binding sites in the mitochondrial fraction of rat testis is described. The dissociation constant (KD) from saturation studies was 0.16 +/- 0.04 nM. The association and dissociation rate constants (k1 and k-1) were 3.95 +/- 0.57 x 10(8) M(-1) min(-1) and 0.025 +/- 0.002 min(-1), respectively. The number of binding sites was 2,100 +/- 163 fmols/mg protein. [3H] NBMPR binding was inhibited, in a nanomolar range, by NBMPR (KI= 0.23 +/- 0.02 nM), OH-NBMPR (KI= 2.30 +/- 0.55 nM) and HNBTG (KI= 2.58 +/- 0.33 nM). In the micromolar range, adenosine receptor ligands such as PIA (3.46 +/- 1.36 microM), 2-chloroadenosine (18.81 +/- 3.36 microM) and NECA (8.26 +/- 3.90 microM), and mitochondrial benzodiazepine receptor ligands such as Ro 5-4864 (5.15 +/- 1.82 micrmoM and PK 11195 inhibited the specific binding of [3H] NBMPR. These results suggest the existence of a nucleoside transport system in the mitochondrial fraction of rat testis.
Camins
A
A
Laboratory of Pharmacology and Pharmacognosy, Faculty of Pharmacy, University of Barcelona, Spain.
Jimenez
A
A
Sureda
F X
FX
Pallàs
M
M
Escubedo
E
E
Camarasa
J
J
D000345:Affinity Labels / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D015394:Molecular Structure; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity; D013737:Testis / Q000378:metabolism*; D013868:Thioinosine / Q000031:analogs & derivatives* / Q000378:metabolism; D014316:Tritium
D000345:Affinity Labels; D002352:Carrier Proteins; D014316:Tritium; D013868:Thioinosine; C001789:4-nitrobenzylthioinosine