[125I]Endothelin-1 binds to a single class of high-affinity binding sites in rat cardiac membranes (KD 0.20 nM, Bmax 93.5 fmol/mg protein) distinct from known calcium channel regulators.
Endothelin-1 binds to a specific high-affinity receptor in rat cardiac membranes that is distinct from voltage-activated calcium channels.
Standard binding and displacement techniques were used to identify high-affinity binding sites for 125I-labeled endothelin-1 (ET-1) in membranes harvested from the hearts of adult female Sprague-Dawley rats. A single population of binding sites was identified, with a KD of 0.20 +/- 0.03 nM at 37 degrees C, and a Bmax of 93.5 +/- 6.4 fmol/mg protein. Bound 125IET-1 was displaced by ET-1 (10(-13)-10(-8) M), with a Ki of 0.08 nM. Neither (-)Bay K 8644 (10(-11)-10(-5) M), prenylamine (10(-11)-10(-5) M), (+)-cis-diltiazem (10(-10)-10(-5) M), (-)D888 (10(-10)-10(-5) M), nicardipine (10(-10)-10(-5) M), lidoflazine (10(-11)-10(-5) M), flunarizine (10(-11)-10(-5) M), omega-conotoxin (10(-13)-10(-7) M), nor prazosin (10(-10)-10(-5) M) displaced the bound ligand. Binding occurred in the absence of Ca2+ and was absent in heat-denatured membranes. These results are interpreted to mean that 125IET-1 binds to a single class of high-affinity binding sites that differ from those occupied by known regulators of voltage activated L- and N-type Ca2+ channels.
Gu et al. (1989) studied this question. [125I]Endothelin-1 was evaluated on Binding characteristics (KD and Bmax). [125I]Endothelin-1 binds to a single class of high-affinity binding sites in rat cardiac membranes (KD 0.20 nM, Bmax 93.5 fmol/mg protein) distinct from known calcium channel regulators.