PT - JOURNAL ARTICLE AU - M E Torres-Márquez AU - M T Romero-Avila AU - C González-Espinosa AU - J A García-Sáinz TI - Characterization of rat white fat cell alpha 1B-adrenoceptors. DP - 1992 Sep 01 TA - Molecular Pharmacology PG - 403--406 VI - 42 IP - 3 4099 - http://molpharm.aspetjournals.org/content/42/3/403.short 4100 - http://molpharm.aspetjournals.org/content/42/3/403.full SO - Mol Pharmacol1992 Sep 01; 42 AB - In isolated rat white adipocytes, epinephrine (in the presence of 10 microM propranolol) increased the uptake of [32P]Pi into phosphatidylinositol in a dose-dependent fashion. When the cells were pretreated with the irreversible antagonist chlorethylclonidine, this alpha 1-adrenergic effect was markedly diminished. The effect of epinephrine was dose-dependently antagonized by selective alpha 1-adrenergic antagonists, with the potency order prazosin greater than 5-methylurapidil greater than or equal to WB4101. Binding studies using crude membrane preparations were performed with the ligands [3H]bunazosin and 125I-HEAT. Both ligands bound to membrane sites with high affinity (Kd values of 0.75 +/- 0.20 nM for [3H]bunazosin and 125 +/- 20 pM for 125I-HEAT), in a rapid, reversible, and saturable (Bmax, 9-12 fmol/mg of protein) fashion, and with the expected pharmacological characteristics for alpha 1-adrenoceptors. Binding displacement studies with these ligands indicated a potency order of prazosin greater than 5-methylurapidil greater than or equal to WB4101. Northern blot analysis using receptor subtype-specific gene probes showed that adipocyte mRNA hybridized with the alpha 1B-adrenergic probe. All these data suggest that the alpha 1-adrenoceptors of rat white adipocytes belong to the alpha 1B subtype.