Solubilization of Active Brain α1-Adrenoceptors by a Zwitterionic Detergent

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Abstract
Solubilization of rat brain .alpha.1-adrenoceptors was performed by treatment with 6 mM CHAPS (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate). The .alpha.1-adrenoceptor antagonist [3H]prazosin was shown to bind reversibly and sepcifically to the soluble extract obtained after centrifugation at 150,000 .times. g for 1 h. Separation of the soluble [3H]prazosin-bound complexes was performed by the polyethylene glycol precipitation technique followed by filtration. A Scatchard plot of the concentration-dependent binding curve showed only 1 class of binding sites, with a high affinity for [3H]prazosin. Affinity of the solubilized receptors for the ligand increased as the CHAPS concentration in the assay medium decreased; the number of binding sites remained unchanged (.simeq. 70 fmol/mg protein). This corresponds to a 30% recovery of original membrane sites. The solubilized receptors presented the same chracteristics of specificity and stereospecificity as membrane .alpha.1-adrenoceptors. Moreover, 150 mM NaCl modulated the affinity of epinephrine for the [3H]prazosin-bound soluble complex, as previously described for membrane preparations. CHAPS may be a suitable detergent for solubilizing rat brain .alpha.1-adrenoceptors and preserving their functional activities.

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