title: Characterization of the alpha 1-adrenergic receptor subtype in a smooth muscle cell line.
abstract: We have identified in the DDT1 smooth muscle cell line a [3H]dihydroergocryptine-binding site having the characteristics of an alpha 1-adrenergic receptor. Specific binding of [3H]dihydroergocryptine to DDT1 cells grown either in monolayer or suspension culture was reversible, saturable, and of high affinity, and the binding site demonstrated stereoselectivity. [3H]Dihydroergocryptine dissociation constants of 1.4 +/- 0.2 nM and 1.4 +/- 0.3 nM were observed for suspension and monolayer cells, respectively. However, the concentration of binding sites in suspension-cultured cells (65,100 +/- 8,300 sites/cell) was significantly greater (p less than 0.001) than that found in monolayer cells (27,900 +/- 4,300 sites/cell). The order of agonist competition for the binding site was epinephrine (Ki = 0.92 +/- 0.32 microM) greater than or equal to norepinephrine (Ki = 2.2 +/- 1.0 microM) greater than isoproterenol (Ki = 137 +/- 17 microM), consistent with an alpha-adrenergic interaction. Results of competition experiments with specific antagonists prazosin (alpha 1-selective) or yohimbine (alpha 2-selective) and a computer modeling technique indicated that the alpha-adrenergic receptor of the DDT1 cell was predominantly (greater than 95%) the alpha 1-subtype.
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D006224:Cricetinae; D004088:Dihydroergotoxine / Q000378:metabolism; D007700:Kinetics; D007890:Leiomyosarcoma; D008297:Male; D008647:Mesocricetus; D009130:Muscle, Smooth / Q000378:metabolism*; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*
chemical_list: D000316:Adrenergic alpha-Agonists; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D004088:Dihydroergotoxine