Abstract: This report describes the uptake of l-[propyl-2,3-3H]dihydroalprenolol, a β-adrenergic antagonist, by HeLa (human adenocarcinoma) cells. [3H]Dihydroalprenolol binds to sites of high capacity and low affinity in intact HeLa cells. The binding achieves equilibrium rapidly and is rapidly reversible. Bound [3H]dihydroalprenolol is displaceable by β-adrenergic antagonists in a nonstereoselective fashion, but is not displaceable by isoproterenol, an adrenergic agonist. Phentolamine, an α-adrenergic antagonist, and chloroquine, a lysosomotropic amine, also compete for [3H]dihydroalprenolol binding sites. [3H]Dihydroalprenolol binding is inhibited by metabolic inhibitors, but not by cytoskeletal blocking agents. The binding is sensitive to extracellular pH (less binding at lower pH) and is temperature-sensitive (less binding at lower temperatures). The bound radioligand is rapidly reversed following hypotonic lysis of the cells. These [3H]dihydroalprenolol binding sites in intact HeLa cells therefore do not have the characteristics expected for β-adrenergic receptors. Further studies showed that β-adrenergic receptors could be detected in a HeLa membrane preparation using [125I]iodohydroxybenzylpindolol, and that chloroquine had very low affinity for these receptors. We conclude that [3H]dihydroalprenolol diffuses across the plasma membrane of intact HeLa cells and accumulates in acidic intracellular compartments.

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   |wiki=    Sante
   |area=    ChloroquineV1
   |flux=    Main
   |étape=   Exploration
   |type=    RBID
   |clé=     ISTEX:9494A65CD33977DDA54050C0DC4A18C6A2286896
   |texte=   Uptake of l-[ propyl -2,3-3H]dihydroalprenolol by intact HeLa cells
}}