Alpha-1 adrenergic receptor binding in aortas from rat and dog: comparison of [3H]prazosin and beta-iodo-[125I]-4-hydroxyphenyl-ethyl-aminomethyl-tetralone

J Pharmacol Exp Ther. 1987 Jun;241(3):875-81.


We have identified and characterized pharmacologically alpha-1 adrenergic receptors in aorta from dog and rat utilizing two alpha-1 antagonists, [3H]prazosin and beta-3-iodo[125I]-4-hydroxyphenyl-ethyl-aminoethyl-tetralone [125I]HEAT, to determine receptor number and affinity. The rat and dog alpha-1 receptors were found to be very similar. In the dog, KD values were 27 and 11 pM for [3H]prazosin and [125I]HEAT, respectively, whereas maximum binding values were 89 and 65 fmol/mg of protein. KD values in rat aorta were 22 and 15 pM for [3H]prazosin and [125I]HEAT, respectively, whereas maximum binding values were 62 and 47 fmol/mg of protein. Both tissues demonstrated a rank order potency of antagonist inhibition of the two radioligands consistent with an alpha-1 adrenergic receptor with prazosin greater than phentolamine greater than yohimbine. A comparison between IC50 values for both the ligands and the tissues shows strong correlations suggesting the two radioligands are identifying a similar receptor population and that the receptor labeled by the ligands has similar pharmacologic characteristics in the two tissues.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adrenergic alpha-Antagonists / pharmacology
  • Animals
  • Aorta / metabolism*
  • Dogs
  • Kinetics
  • Phenethylamines / pharmacology*
  • Phentolamine / pharmacology
  • Prazosin / pharmacology*
  • Rats
  • Rats, Inbred Strains
  • Receptors, Adrenergic, alpha / metabolism*
  • Tetralones*
  • Yohimbine / pharmacology


  • Adrenergic alpha-Antagonists
  • Phenethylamines
  • Receptors, Adrenergic, alpha
  • Tetralones
  • Yohimbine
  • 2-(beta-(3-iodo-4-hydroxyphenyl)ethylaminomethyl)tetralone
  • Prazosin
  • Phentolamine