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  • Title: Subtypes of alpha 1-adrenoceptors in DDT1 MF-2 and BC3H-1 clonal cell lines.
    Author: Han C, Esbenshade TA, Minneman KP.
    Journal: Eur J Pharmacol; 1992 Jun 05; 226(2):141-8. PubMed ID: 1353451.
    Abstract:
    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.
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