[H-3] P-AMINOCLONIDINE AND [H-3] IDAZOXAN LABEL DIFFERENT POPULATIONS OF IMIDAZOLINE SITES ON RAT-KIDNEY

被引:45
作者
MACKINNON, AC [1 ]
STEWART, M [1 ]
OLVERMAN, HJ [1 ]
SPEDDING, M [1 ]
BROWN, CM [1 ]
机构
[1] UNIV EDINBURGH, DEPT PHARMACOL, EDINBURGH EH8 9JZ, MIDLOTHIAN, SCOTLAND
关键词
H-3]P-AMINOCLONIDINE; H-3]IDAZOXAN; IMIDAZOLINE BINDING SITES; RS-15385-197; KIDNEY (RAT);
D O I
10.1016/0014-2999(93)90731-V
中图分类号
R9 [药学];
学科分类号
1007 ;
摘要
In the presence of RS-15385-197 to preclude binding to alpha2-adrenoceptors, [H-3]p-aminoclonidine labelled a low affinity high capacity site, (K(d) = 127.6 +/- 19.7 nM, B(max) 978 +/- 172 fmol/mg protein) whereas [H-3]idazoxan labelled a high affinity low capacity site (K(d) = 1.66 +/- 0.28 nM, B(max) 45.3 +/- 11.4 fmol/mg protein). Clonidine and p-aminoclonidine showed moderate affinity for the site labelled by [H-3]p-aminoclonidine, but low affinity for the site labelled by [H-3]idazoxan, whereas idazoxan showed high affinity for [H-3]idazoxan and low affinity for [H-3]p-aminoclonidine binding. Naphazoline inhibited [H-3]idazoxan in a biphasic manner suggesting that [H-3]idazoxan may label an heterogeneous population of imidazoline sites. GTP inhibited [H-3]idazoxan but not [H-3]p-aminoclonidine binding. These results suggest that [H-3]idazoxan labelled imidazoline I2 binding sites, whereas [H-3]p-aminoclonidine labelled a novel subtype which showed marked differences to the imidazoline I1 binding site reported in bovine and human brainstem.
引用
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页码:79 / 87
页数:9
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