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Title: Identification and characterization of a putative human platelet thromboxane A/sub 2//prostaglandin H/sub 2/ receptor

The thromboxane A/sub 2/ (TXA/sub 2/) analog, 9,11-dimethylmethano-11,12-methano-16-(3-iodo-4-hydroxyphenyl)-13,14-dihydro-13-aza-15..cap alpha beta..-omega-tetranor TXA/sub 2/ (I-PTA-OH) was characterized as a competitive antagonist of TXA/sub 2/ mimetic-induced platelet aggregation, with a K/sub d/ of 190 nM in platelet rich plasma. This antagonism was specific for the putative thromboxane A/sub 2//prostaglandin H/sub 2/ (TXA/sub 2//PGH/sub 2/) receptor, since I-PTA-OH had no inhibitory effects on platelet aggregation stimulated by agonists which act independently of TXA/sub 2//PGH/sub 2/, and did not inhibit platelet TXA/sub 2/ synthesis. (/sup 125/I)-PTA-OH binding to a particulate fraction from human platelets was saturable, displaceable, and linear with protein concentration. Scatchard analysis of equilibrium binding revealed a single class of high affinity binding sites, with a K/sub d/ of 30 +/- 4 nM and a B/sub max/ of 1.8 +/- 0.3 pmol/mg protein. Kinetic analysis yielded a k/sub 1/ of 1.35 x 10/sup 6/ M/sup -1/ x min/sup -1/ and a k..sqrt../sub 1/ of 0.032 min/sup -1/, K/sub d/ = k..sqrt../sub 1//k/sub 1/ = 24 nM. The subcellular localization of the putative TXA/sub 2//PGH/sub 2/ receptor was determined using (/sup 125/I)-PTA-OH binding as a marker for the receptor. (/sup 125/I)-PTA-OH binding as a marker for the receptor. (/sup 125/I)-PTA-OH binding, was coenriched withmore » markers for plasma membranes and dense tubular system; but not with markers for cytoplasmic constituents, mitochondria, or granules.« less
Authors:
Publication Date:
OSTI Identifier:
6550635
Resource Type:
Thesis/Dissertation
Resource Relation:
Other Information: Thesis (Ph. D)
Publisher:
Medical Univ. of South Carolina,Charleston, SC
Research Org:
Medical Univ. of South Carolina, Charleston (USA)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; BLOOD PLATELETS; BLOOD COAGULATION; PROSTAGLANDINS; BIOCHEMICAL REACTION KINETICS; RECEPTORS; CHEMICAL COMPOSITION; BIOLOGICAL MARKERS; CELL MEMBRANES; IODINE 125; MAN; TRACER TECHNIQUES; ANIMALS; BETA DECAY RADIOISOTOPES; BIOLOGICAL MATERIALS; BLOOD; BLOOD CELLS; BODY FLUIDS; CELL CONSTITUENTS; DAYS LIVING RADIOISOTOPES; ELECTRON CAPTURE RADIOISOTOPES; INTERMEDIATE MASS NUCLEI; IODINE ISOTOPES; ISOTOPE APPLICATIONS; ISOTOPES; KINETICS; MAMMALS; MATERIALS; MEMBRANE PROTEINS; MEMBRANES; NUCLEI; ODD-EVEN NUCLEI; ORGANIC COMPOUNDS; PRIMATES; PROTEINS; RADIOISOTOPES; REACTION KINETICS; VERTEBRATES 550201* -- Biochemistry-- Tracer Techniques