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Amphibian myocardial angiotensin II receptors are distinct from mammalian AT 1 and AT 2 receptor subtypes
Author(s) -
Sandberg Kathryn,
Ji Hong,
Millan Monica A.,
Catt Kevin J.
Publication year - 1991
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(91)80704-7
Subject(s) - receptor , dithiothreitol , angiotensin ii , amphibian , peptide , xenopus , angiotensin receptor , chemistry , binding site , medicine , biology , endocrinology , microbiology and biotechnology , biochemistry , enzyme , gene , ecology
High‐affinity receptors for angiotensin II were identified on Xenopus laevis cardiac membranes and characterized by binding‐inhibition studies with peptide and non‐peptide AII antagonists. Scatchard analysis of the binding data identified a high‐affinity site with K d1 =1.6 nM and B max1 =3.7 pmol/mg protein and a low‐affinity site with K d2 =22 nM and B max2 =9.5 pmol/mg protein. Treatment with dithiothreitol reduced the number of binding sites by > 70%. The rank order of potency for AII analogs was (agent, IC 50 ) [Sar 1 ,Ile 8 ]AII, 0.91 nM > AII, 2.0 nM > AI, 5.3 nM > [Sar 1 , Ala 8 ]AII, 19 nM > CGP42112A, 1.2 μM ⋙ DuP 753≈PD‐123177, > μM. The relative potencies of these compounds differ markedly from their activities on the two known mammalian AII receptor subtypes, AT 1 and AT 2 . These results indicate that amphibian AII receptors are pharmacologically distinct from both the AT 1 and AT 2 receptors characterized in mammalian tissues.