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Characterization of two new ET B selective radioligands, [ 125 I]‐BQ3020 and [ 125 I]‐[Ala 1,3,11,15 ]ET‐1 in human heart
Author(s) -
Molenaar Peter,
Kuc Rhoda E.,
Davenport Anthony P.
Publication year - 1992
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1992.tb14498.x
Subject(s) - ventricle , stereochemistry , receptor , chemistry , medicine , biochemistry
Two new endothelin receptor radioligands, [ 125 I]‐BQ3020 and [ 125 I]‐[Ala 1,3,11,15 ]ET‐1, were characterized in tissue sections of human right atrium and left ventricle. Both radioligands had high affinity ([ 125 I]‐BQ3020 right atrium: K D = 0.145 ± 0.037 n m , left ventricle: K D = 0.107 ± 0.004 n m ; [ 125 I]‐[Ala 1,3,11,15 ]ET‐1 right atrium: K D = 0.239 ± 0.036 n m , left ventricle: K D = 0.199 ± 0.027 n m ). Competition binding experiments were performed in the left ventricle. The selective ET A receptor compound BQ123 competed with low affinity against [ 125 I]‐BQ3020 ( K D = 28.7 ± 2.7 μ m ) and [ 125 I]‐[Ala 1,3,11,15 ]ET‐1 ( K D = 28.5 ± 4.2 μ m ). The selective ET B receptor compound BQ3020 competed with high affinity against [ 125 I]‐BQ3020 ( K D = 40.8 ± 6.6 p m ) and [ 125 I]‐[Ala 1,3,11,15 ]ET‐1 ( K D = 0.276 ± 0.099 n m ). Another selective ET B receptor compound, [Ala 1,3,11,15 ]ET‐1 also competed with high affinity against [ 125 I]‐BQ3020 ( K D = 0.663 ± 0.120 n m ) and [ 125 I]‐[Ala 1,3,11,15 ]ET‐l ( K D = 0.643 ± 0.124 n m ). These results indicate that [ 125 I]‐BQ3020 and [ 125 I]‐[Ala 1,3,11,15 ]ET‐1 are selective ET B receptor radioligands. [Ala 1,3,11,15 ]ET‐1 competed with the non‐selective radioligand [ 125 I]‐ET‐1 in left ventricle and revealed the presence of ET A and ET B receptors in the proportions of 76:24% respectively in the human left ventricle.