Evidence for the participation of disulfide and sulfhydril groups in the specific binding of [3H]prazosin in cerebral cortex |
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Authors: | Tomás A. Reader Richard Brière |
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Affiliation: | (1) Centre de recherche en sciences neurologiques Département de physiologie Faculté de Médecine, Université de Montréal, H3C 3J7 Montréal, Québec, Canada |
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Abstract: | The tritiated 1 antagonist prazosin [3H]PRZ binds specifically and with high affinity to postsynaptic adrenoceptors in membrane preparations from cerebral cortex. Since adrenoceptors are of protein nature, it was of interest of investigate the possible role of disulfide (—SS—) and sulfhydril (—SH) groups in the binding of [3H]PRZ. Pretreatment of the membranes with the disulfide and sulfhydryl reactivesdl0Dithiothreitol,l-Dithiothreitol, Dithioerythritol or 5,5-Dithiobis-(2-nitrobenzoic acid) (DTNB), alone or in combination with the alkylating agent N-Methylmaleimide (NMM), decreased specific [3HPRZ binding, with minor changes in the non-specific counts. Saturation experiments revealed that all these reagents reduced the affinity of the binding site for [3H]PRZ, as judged by theKd 25°C, but only the alkylating agent NMM and the oxydizing reagent DTNB produced in addition to the increase inKd, a decrease of the maximum binding capacity (Bmax). The present results provide evidence for a participation of—SS—and/or—SH groups in the recognition site of the 1-adrenoceptor of cerebral cortex. |
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