Characterization and autoradiographic localization of [3H] alpha,beta-methylene ATP binding sites in cat urinary bladder.
1. The characteristics and distribution of [3H] alpha,beta-methylene ATP ([3H] alpha,beta-MeATP), a radioligand for P2X-purinoceptors, binding sites in cat urinary bladder detrusor were examined. 2. Saturation analysis revealed that, in cat bladder membrane preparations, only one population of binding sites with high affinity (Kd = 1.8 nM) was present, in contrast to other species where both high-and low-affinity binding sites are present. Another feature is that the density of the binding sites in the cat bladder (Bmax = 21.2 pmol/mg protein) is considerably higher (about 2-fold) than the high-affinity binding component in the rat bladder membrane preparations. 3. Displacement experiments with unlabelled purinoceptor ligands indicate that [3H] alpha,beta-MeATP mainly binds to P2X-purinoceptors. The order of binding displacement activity was: alpha,beta-methylene ATP, beta,gamma-methylene ATP > 2-methylthioATP > ATP > suramin and L-beta,gamma-methylene ATP > > adenosine. 4. Autoradiographic study demonstrated dense specific binding sites of [3H] alpha,beta-MeATP on detrusor smooth muscle of cat bladder. 5. The results of this study are consistent with pharmacological studies for the existence of P2X-purinoceptors in cat bladder.
Zhao
M
M
Department of Anatomy and Developmental Biology, University College London, UK.
Bo
X
X
Neely
C F
CF
Burnstock
G
G
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism / Q000493:pharmacokinetics; D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D002415:Cats; D066298:In Vitro Techniques; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D011869:Radioligand Assay; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D001743:Urinary Bladder / Q000378:metabolism*
D018048:Receptors, Purinergic P2; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate