Binding of a thromboxane A2 (TXA2)/prostaglandin H2 (PGH2) receptor antagonist to rabbit and pig heart membrane protein.
This study aimed at testing the hypothesis that the binding sites for TXA2/PGH2 are present and different in the heart as compared to platelets and blood vessels. Kinetic studies on the thromboxane binding to protein of membrane preparations from rabbit and pig hearts were carried out using [125I]-PTA-OH, a potent specific thromboxane receptor antagonist. The following points are stressed: 1. the binding sites to 125I-PTA-OH were shown to be present in the heart membrane whatever the adopted experimental conditions were i.e. the temperature (4 or 30 degrees C) used for incubation the protein fractions under study: either the 105,000 g supernatant or the 200,000 g supernatant of the solubilized pellet (105,000 g) the animal species: rabbit and pig 2. the radioligand binding was rapid, saturable and reversible 3. the kinetically determined Kd's were in the picomolar range--11 and 14 pM for the rabbit and pig heart membrane preparation respectively--instead of the nanomolar range found in other tissues of the nanomolar range found in other tissues--27-39 nM and 2 nM for human platelets and bovine artery endothelial cells respectively- using the same thromboxane receptor antagonist.
Lasserre
B
B
Pharmacologie de la Régulation', Institut de Physiologie, Toulouse, France.
Huu
A P
AP
Navarro-Delmasure
C
C
Dossou-Gbete
V
V
D000818:Animals; D001665:Binding Sites; D007700:Kinetics; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D009928:Organ Specificity; D011817:Rabbits; D011982:Receptors, Prostaglandin / Q000037:antagonists & inhibitors*; D017482:Receptors, Thromboxane / Q000037:antagonists & inhibitors*; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D013552:Swine; D013928:Thromboxane A2 / Q000031:analogs & derivatives* / Q000378:metabolism
D008565:Membrane Proteins; D011982:Receptors, Prostaglandin; D017482:Receptors, Thromboxane; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D013928:Thromboxane A2; C046957:I-PTA-OH