Subtypes of alpha 1-adrenoceptors in DDT1 MF-2 and BC3H-1 clonal cell lines.
We examined which subtype(s) of alpha 1-adrenoceptors are expressed in the widely used DDT1 MF-2 and BC3H-1 cell lines. Pretreatment with chloroethylclonidine (CEC) inactivated 76-85% of the specific [125I]BE 2254 binding sites in membrane preparations from both cell lines. Competition with subtype-selective competitive antagonists showed primarily the alpha 1B subtype in both cell lines. However, in BC3H-1 cells 5-methyl-urapidil showed complex behavior suggesting that about half of the binding sites had a lower affinity. Chloroethylclonidine pretreatment eliminated [3H]inositol phosphate responses to norepinephrine in both cell lines. Measurement of intracellular Ca2+ with fura-2 in DDT1 MF-2 cells showed that norepinephrine induced a complex response involving both transient and sustained components. Chloroethylclonidine pretreatment blocked both responses, while chelation of extracellular Ca2+ left the transient response intact but eliminated the sustained component. These results support previous work that these cell lines contain alpha 1B-adrenoceptors linked to inositol phosphate formation and mobilization of intracellular Ca2+. However, these results show that alpha 1B-adrenoceptors can be linked to Ca2+ influx as well as intracellular mobilization, and support the existence of pharmacologically distinct alpha 1B variants.
Han
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Department of Pharmacology, Emory University Medical School, Atlanta, GA 30322.
Esbenshade
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Minneman
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D000317:Adrenergic alpha-Antagonists / Q000378:metabolism; D001667:Binding, Competitive / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003000:Clonidine / Q000031:analogs & derivatives / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects; D009638:Norepinephrine / Q000378:metabolism; D010627:Phenethylamines / Q000378:metabolism; D010879:Piperazines / Q000378:metabolism; D011869:Radioligand Assay; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*; D044024:Tetralones
D000317:Adrenergic alpha-Antagonists; D007295:Inositol Phosphates; D010627:Phenethylamines; D010879:Piperazines; D011942:Receptors, Adrenergic, alpha; D044024:Tetralones; C057446:5-methylurapidil; C051731:chlorethylclonidine; C010652:BE 2254; D003000:Clonidine; D002118:Calcium; D009638:Norepinephrine