title: Characteristics and metabolism of alpha 1 adrenergic receptors in a nonfusing muscle cell line.
abstract: The BC3H1 nonfusing muscle cell line possesses binding sites for [3H]prazosin. These binding sites are typically alpha 1 adrenergic receptors as shown by their greater affinity (3700-fold) for prazosin than for yohimbine. Both kinetic and equilibrium analyses indicated that [3H]prazosin interacted with only one category of independent binding sites with the following characteristics. KD = 0.13 +/- 0.01 nM. Bmax = 97 +/- 5 fmol/mg of protein corresponding to 25,000 sites/cell (n = 17). Biosynthesis of the alpha 1 adrenergic receptor was investigated at cell confluency (when the number of cells and their total protein content were constant). Phenoxybenzamine (10(-9) M) irreversibly blocked 50% of the alpha 1 receptors in intact cells. More than 95% blockade of receptors was obtained with 10(-7) M phenoxybenzamine. After this blockade, new alpha 1 adrenergic receptors reappeared in the cells with monoexponential kinetics. These new receptors corresponded to synthesized receptors since their appearance was blocked by cycloheximide (1 micrograms/ml). The cycloheximide action was reversible. If one makes the simple and probable hypotheses that the receptor production is constant and that degradation is a monoexponential process, the analysis of the kinetics of reappearance allows the determination of the rate constant for receptor degradation (k = 0.03 h-1) and the rate of receptor production (r = 3.2 fmol/mg/h) corresponding to the synthesis of about 760 receptors/cell/h. The half-life of the receptor was 23 h.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002459:Cell Fusion; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D009132:Muscles; D010643:Phenoxybenzamine / Q000494:pharmacology; D011224:Prazosin / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*
chemical_list: D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D010643:Phenoxybenzamine; D003513:Cycloheximide; D011224:Prazosin