title: Photoaffinity labelling of a thromboxane A2/prostaglandin H2 antagonist binding site in human platelets.
abstract: The diazonium salt of 9,11-dimethylmethano-11,12-methano-16-(4-aminophenoxy)13,14- dihydro-13-aza-15 alpha beta-omega-tetranor TXA2 (PTA-POA) was synthesized and used as a photoaffinity ligand for the putative human platelet TXA2/PGH2 receptor. Incubation of human platelet membranes with the diazonium salt of PTA-POA followed by photolysis at 290 nm(hv) resulted in a 40% decrease in the specific binding of [125I]PTA-OH as measured in the radioligand binding assay. Co-incubation with a TXA2/PGH2 agonist followed by photolysis resulted in no decrease in specific binding. Incubation of the diazonium salt of PTA-POA with solubilized platelet membranes without photolysis followed by Scatchard analysis resulted in no change in the Kd for [125I]PTA-OH (38 nM) and the preparation which was incubated with the diazonium salt (42 nM). However, the Bmax for [125I]PTA-OH binding was reduced from 2.4 pmole/mg protein for control to 1.4 pmole/mg protein. These studies show that the diazonium salt of PTA-POA may be a useful photoaffinity ligand for human platelet TXA2/PGH2 receptors.
mesh_terms: D000345:Affinity Labels / Q000494:pharmacology*; D001792:Blood Platelets / Q000032:analysis*; D006801:Humans; D010782:Photolysis; D011449:Prostaglandin Endoperoxides / Q000037:antagonists & inhibitors*; D011450:Prostaglandin Endoperoxides, Synthetic / Q000037:antagonists & inhibitors*; D044262:Prostaglandin H2; D011463:Prostaglandins H / Q000037:antagonists & inhibitors*; D011982:Receptors, Prostaglandin / Q000032:analysis*; D017482:Receptors, Thromboxane; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D013928:Thromboxane A2 / Q000037:antagonists & inhibitors*
chemical_list: D000345:Affinity Labels; D011449:Prostaglandin Endoperoxides; D011450:Prostaglandin Endoperoxides, Synthetic; D011463:Prostaglandins H; D011982:Receptors, Prostaglandin; D017482:Receptors, Thromboxane; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D044262:Prostaglandin H2; D013928:Thromboxane A2