Characterization of alpha-2 adrenergic receptors in the OK cell, an opossum kidney cell line

J Pharmacol Exp Ther. 1988 Feb;244(2):571-8.


We have characterized alpha-2 adrenergic receptors in OK cells, an opossum kidney-derived cell line. In membrane saturation binding experiments, [3H]rauwolscine (Kd = 74 pM) was 3-fold more potent than [3H]yohimbine (Kd = 230 pM). Each labeled a single class of binding sites with densities of 135 and 124 fmol/mg of protein for [3H]rauwolscine and [3H]yohimbine, respectively. Inhibition of [3H]rauwolscine and [3H]yohimbine binding by several alpha adrenergic agonists and antagonists demonstrated the radioligands labeled an alpha-2 type adrenergic receptor with a pharmacological profile similar to the alpha-2B receptor subtype. The rank order of potency for antagonist inhibition of binding was yohimbine greater than prazosin = phentolamine greater than chlorpromazine = corynanthine, whereas the rank order of agonist potency was oxymetazoline = clonidine greater than or equal to UK-14,304 greater than or equal to (-)-epinephrine greater than (-)-norepinephrine. The oxymetazoline, clonidine and antagonist inhibition curves were routinely monophasic and modeled best as a single class of binding sites. For the other agonists, inhibition binding curves were biphasic with approximately 35% of the binding sites existing in a high affinity state. These curves were shifted to the right in the presence of 0.1 mM GTP, and in general modeled as a single class of binding sites. UK-14,304, (-)-epinephrine, (-)-norepinephrine and oxymetazoline attenuated parathyroid hormone-stimulated cyclic AMP production by up to 70% in whole cell monolayers in a dose-dependent manner via a pertussis toxin-sensitive mechanism. With the exception of oxymetazoline, this inhibition could be reversed with alpha adrenergic antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adrenergic alpha-Agonists / pharmacology
  • Adrenergic alpha-Antagonists / pharmacology
  • Animals
  • Brimonidine Tartrate
  • Cell Line
  • Cyclic AMP / biosynthesis
  • Kidney / analysis*
  • Kinetics
  • Opossums
  • Parathyroid Hormone / pharmacology
  • Quinoxalines / metabolism
  • Receptors, Adrenergic, alpha / analysis*
  • Yohimbine / metabolism


  • Adrenergic alpha-Agonists
  • Adrenergic alpha-Antagonists
  • Parathyroid Hormone
  • Quinoxalines
  • Receptors, Adrenergic, alpha
  • Yohimbine
  • Brimonidine Tartrate
  • Cyclic AMP