title: Human erythroleukemia cells express functional thromboxane A2/prostaglandin H2 receptors.
abstract: The human erythroleukemia (HEL) cell line is a cultured hematopoietic cell line reported to express platelet membrane glycoproteins and alpha-2 adrenergic receptors. The present studies were designed to determine if functional thromboxane A2 (TXA2)/prostaglandin H2 (PGH2) receptors exist in HEL cells. Radioligand binding assays were performed using [125I]PTA-OH, a TXA2/PGH2 receptor antagonist. Scatchard analysis revealed one class of binding sites for 1-PTA-OH with a Kd = 122 +/- 18 nM and maximum binding = 1.7 +/- 0.3 x 10(5) sites/cell. Competition for [125I]PTA-OH binding with the TXA2/PGH2 receptor agonists SQ26655 and U46619 revealed one class of binding sites for SQ26655 with a Kd = 17 nM and two classes of binding sites for for U46619 with a Kd = 45 nM for the high-affinity site and a Kd = 450 nM for the low-affinity site. Competition for [125I]PTA-OH by the steroisomeric TXA2/PGH2 receptor antagonists L657925 and L657926 revealed two classes of binding sites for the more potent L657925 with a Kd = 8 nM for the high-affinity site and a Kd = 400 nM for the low-affinity site whereas L657926 bound to one class of sites with a Kd = 380 nM. Stimulation of the TXA2/PGH2 receptor by SQ26655 and U46619 resulted in concentration-dependent increases in [Ca++], as measured by FURA-2 fluorescence, with EC50 values of 28 +/- 2 and 149 +/- 32 nM, respectively. I-PTA-OH, L657925 and L657926 antagonized this response to U46619 with IC50 values similar in rank potency to that seen in the binding studies.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston.
authors.forename: P R
authors.initials: PR
authors.lastname: Mayeux
authors.forename: D E
authors.initials: DE
authors.lastname: Mais
authors.forename: C
authors.initials: C
authors.lastname: Carr
authors.forename: P V
authors.initials: PV
authors.lastname: Halushka
mesh_terms: D002118:Calcium / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute / Q000503:physiopathology*; D011450:Prostaglandin Endoperoxides, Synthetic / Q000502:physiology; D044262:Prostaglandin H2; D011463:Prostaglandins H / Q000502:physiology; D011869:Radioligand Assay; D011982:Receptors, Prostaglandin / Q000187:drug effects / Q000502:physiology*; D017482:Receptors, Thromboxane; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D013928:Thromboxane A2 / Q000502:physiology; D013929:Thromboxane B2 / Q000096:biosynthesis; D014407:Tumor Cells, Cultured
chemical_list: D011450:Prostaglandin Endoperoxides, Synthetic; D011463:Prostaglandins H; D011982:Receptors, Prostaglandin; D017482:Receptors, Thromboxane; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D044262:Prostaglandin H2; D013929:Thromboxane B2; D013928:Thromboxane A2; D002118:Calcium; D004121:Dimethyl Sulfoxide