CHARACTERIZATION OF ALPHA-2 ADRENERGIC-RECEPTORS IN THE OK CELL, AN OPOSSUM KIDNEY-CELL LINE

Google Scholar
  • 1 February 1988
    • journal article
    • research article
    • Vol. 244  (2) , 571-578
Abstract
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 or [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 > prazosin = phentolamine > chlorpromazine = corynathine, whereas the rank order of agonist potency was oxymetazoline = clonidine .gtoreq. UK-14,304 .gtoreq. (-)-epinephrine > (-)-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 tonin-sensitive mechanism. With the exception of oxymetazoline, this inhibition could be reversed with alpha adrenergic antagonists. Our findings demonstrate that OK cells express alpha-2 adrenergic receptors negatively coupled to adenylate cyclase. The OK cell appears to be a useful model system for the study of the regulation and mechanism of action of alpha-2 adrenergic receptors in renal tissue.

This publication has 1 reference indexed in Scilit: