Tissue specificity of endothelin binding sites.
A measurement was made of the binding of 125I-labeled endothelin (125I-ET) to crude membrane fractions prepared from rat aorta, atrium, ventricle, portal vein, trachea, lung parenchyma, vas deferens, ileum, bladder, and guinea-pig taenia coli and lung parenchyma. Scatchard analysis of 125I-ET binding in all tissues indicated binding to a single class of saturable sites. The affinity and density of 125I-ET binding sites varied between tissues. The Kd of 125I-ET binding was approximately 0.5 nM for rat aorta, trachea, lung parenchyma, ventricle, bladder, and vas deferens, and guinea-pig taenia coli and lung parenchyma, 1.8 nM for rat portal vein and atrium, and 3.3 nM for ileum. The Bmax of 125I-ET binding had the following rank order of density in rat tissues: trachea greater than lung parenchyma = vas deferens much greater than aorta = portal vein = atrium greater than bladder greater than ventricle = ileum. The properties of 125I-ET endothelin binding were characterized in rat ventricular membranes. 125I-ET binding was time dependent, reaching a maximum within 45-60 min at 25 degrees C. The calculated microassociation constant was 9.67 x 10(5) s-1 M-1. Only 15-20% of 125I-ET dissociated from its binding site even when dissociation was studied as long as 3 h. Preincubation of ventricular membranes with ET prevented binding of 125I-ET. 125I-ET binding was destroyed by boiling of ventricular membranes and was temperature, pH, and cation (Ca2+, Mg2+, and Na+) dependent.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Pharmacology, BioMega, Inc., Laval, Quebec, Canada.
G T
GT
Bolger
F
F
Liard
R
R
Krogsrud
D
D
Thibeault
J
J
Jaramillo
D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D016232:Endothelins / Q000493:pharmacokinetics*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D014018:Tissue Distribution
D016232:Endothelins; D007457:Iodine Radioisotopes