Specific high-affinity binding sites for 125I-labelled porcine endothelin in rat cardiac membranes.
125I-labelled porcine endothelin (125I-endothelin) was used to identify specific high affinity endothelin binding sites in rat cardiac membrane fragments. Binding was to a single population of sites, with a KD of 0.20 +/- 0.03 nM and a Bmax of 93.5 +/- 6.4 fmol/mg protein at 37 degrees C. Reducing the temperature to 25 degrees C increased (P less than 0.02) the KD without changing Bmax. 125I-Endothelin binding was Ca2+ independent. Specific binding was saturable and displaceable by cold endothelin and sarafotoxin S6b, but not by (-)Bay K8644, nicardipine, (-)D888, (+)cis-diltiazem, prenylamine, lidoflazine, flunarizine, nor by 10(-10)-10(-4) M CoCl2, nor 10(-10)-10(-4) M NiCl2. omega-Conotoxin, prazosin, isoprenaline, angiotensin II and its inhibitor, vasopressin and its inhibitor, glyceryl trinitrate, amiloride, ergometrine and FII stonefish toxin also failed to displace bound 125I-endothelin. 10(-4)-10(-2) M CaCl2, 10(-4)-10(-2) M MgCl2, 3 X 10(-6)-10(-3) M MnCl2, 10(-5)-3 X 10(-4) M NiCl2, and 3 X 10(-5)-3 X 10(-4) M CoCl2 stimulated the binding. Incubation at 100 degrees C for 10 min destroyed specific binding.
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Department of Medicine, University of Melbourne, Austin Hospital, Heidelberg, Victoria, Australia.
Casley
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Nayler
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D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002413:Cations, Divalent / Q000494:pharmacology; D016232:Endothelins; D005260:Female; D006358:Hot Temperature; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008566:Membranes / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017466:Receptors, Endothelin; D013552:Swine
D002413:Cations, Divalent; D016232:Endothelins; D007457:Iodine Radioisotopes; D010455:Peptides; D011956:Receptors, Cell Surface; D017466:Receptors, Endothelin