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Characterization of [ 3 H]Clonidine Binding to Two Sites in Calf Brain Membranes
Author(s) -
Braunwalder A.,
Stone G.,
Lovell R. A.
Publication year - 1981
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1981.tb05292.x
Subject(s) - characterization (materials science) , membrane , clonidine , chemistry , biophysics , biology , biochemistry , endocrinology , materials science , nanotechnology
Kinetic studies showed that under appropriate conditions, [ 3 H]clonidine binds to two distinct receptor sites in calf cortex membranes. At 23°C, binding was obtained at a low‐affinity site (dissociation constant, K D = 5.4 n m ) and a high‐affinity site ( K D = 1.1 n m ). In contrast, at 0°C, selective binding occurred to the low‐affinity site only. Consequently, at 0°C, it was possible to evaluate the interaction of drugs with the low‐affinity receptor directly. On the other hand, competition with the high‐affinity receptor could be ascertained by generating displacement curves representing the differential between specific binding values obtained at 23 and 0°C. Guanine nucleotides selectively decreased binding to the high‐affinity site without apparent influence on the low‐affinity [ 3 H]clonidine binding. The activities of various pharmacological agents at the low‐ and high‐affinity clonidine receptors are discussed and compared with WB‐4101 binding data.