A specific binding site for angiotensin II(3-8), angiotensin IV, in rabbit cardiac fibroblasts.
This study demonstrates the existence of a high affinity binding site on rabbit cardiac fibroblasts of the hexapeptide (3-8) fragment of angiotensin II (AngIV). [125I]-AngIV binding is saturable, reversible and distinct from angiotensin II (AngII) receptors. At 37 degrees C equilibrium of [125I]-AngIV binding is reached within 2 h. AngIV displaces [125I]-AngIV bound to cultured rabbit cardiac fibroblasts whereas AngII receptor-specific ligands ([Sar1, Ile8]-AngII, Dup753, CGP42112A) do not. Scatchard plot analysis revealed that [125I]-AngIV binds to a single class of sites with Kd = 4.87 +/- 0.11 x 10(-9) mol/l, Bmax = 371 +/- 8.3 fmol/mg protein and a Hill coefficient of 0.92. In the presence of the non-hydrolyzable GTP analog GTPgammaS [125I]-AngIV binding in rabbit cardiac fibroblasts was not markedly affected, whereas binding of [125I]-(Sar1,IIe8)-AngII is reduced. The role of AngIV in the heart and in particular in cardiac fibroblasts is unknown, and the putative interaction of AngIV with AngII needs further characterization.
Department of Research, Kantonsspital, Basel, Switzerland.
L
L
Wang
M
M
Eberhard
E
E
Kohler
P
P
Erne
D000595:Amino Acid Sequence; D000804:Angiotensin II / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002478:Cells, Cultured; D005347:Fibroblasts / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D011817:Rabbits
D000804:Angiotensin II; C012877:angiotensin II, des-Asp(1)-des-Arg(2)-Ile(5)-