Characterization of rat white fat cell alpha 1B-adrenoceptors.
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.
Torres-Márquez
M E
ME
Departamento de Bioenergética, Universidad Nacional Autónoma de México, D.F.
Romero-Avila
M T
MT
González-Espinosa
C
C
García-Sáinz
J A
JA
D000273:Adipose Tissue / Q000737:chemistry / Q000166:cytology / Q000648:ultrastructure*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D015152:Blotting, Northern; D004837:Epinephrine / Q000494:pharmacology; D007457:Iodine Radioisotopes; D007700:Kinetics; D008297:Male; D008566:Membranes / Q000378:metabolism; D010627:Phenethylamines / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D011799:Quinazolines / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D011942:Receptors, Adrenergic, alpha / Q000032:analysis* / Q000378:metabolism; D013268:Stimulation, Chemical; D044024:Tetralones; D014316:Tritium
D000317:Adrenergic alpha-Antagonists; D007457:Iodine Radioisotopes; D010627:Phenethylamines; D010716:Phosphatidylinositols; D011799:Quinazolines; D012333:RNA, Messenger; D011942:Receptors, Adrenergic, alpha; D044024:Tetralones; D014316:Tritium; C010652:BE 2254; C018176:bunazosin; D011433:Propranolol; D004837:Epinephrine