Alpha-1 adrenergic receptor binding in aortas from rat and dog: comparison of [3H]prazosin and beta-iodo-[125I]-4-hydroxyphenyl-ethyl-aminomethyl-tetralone.
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.
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000378:metabolism*; D004285:Dogs; D007700:Kinetics; D010627:Phenethylamines / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D044024:Tetralones; D015016:Yohimbine / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D010627:Phenethylamines; D011942:Receptors, Adrenergic, alpha; D044024:Tetralones; D015016:Yohimbine; C048008:2-(beta-(3-iodo-4-hydroxyphenyl)ethylaminomethyl)tetralone; D011224:Prazosin; D010646:Phentolamine