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Enhanced Expression of an Endothelin ET A Receptor in Capillaries from Human Glioblastoma: A Quantitative Receptor Autoradiographic Analysis Using a Radioluminographic Imaging Plate System
Author(s) -
Tsutsumi Keisuke,
Niwa Masami,
Kitagawa Naoki,
Yamaga Seiich,
Anda Takeo,
Himeno Akihiko,
Sato Takaya,
Khalid Humayun,
Taniyama Kohtaro,
Shibata Shobu
Publication year - 1994
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1994.63062240.x
Subject(s) - receptor , endothelin receptor , glioblastoma , human brain , endothelin 1 , chemistry , microbiology and biotechnology , biology , pathology , biochemistry , medicine , cancer research , neuroscience
We identified and characterized 125 I‐endothelin‐1 ( 125 I‐ET‐1) binding sites in tumor capillaries isolated from human glioblastomas, using the quantitative receptor autoradiographic technique with pellet sections. Quantification was done using the computerized radioluminographic imaging plate system. High‐affinity ET receptors were localized in capillaries from glioblastomas and the surrounding brain tissues ( K D = 4.7 ± 1.0 × 10 −10 and 1.6 ± 0.3 × 10 −10 M , respectively; B max = 161 ± 38 and 140 ± 37 fmol/mg, respectively; mean ± SEM, n = 5). BQ‐123, a selective antagonist for the ET A receptor, potently competed for 125 I‐ET‐1 binding to sections of the microvessels with IC 50 values of 5.1 ± 0.3 and 5.1 ± 1.5 n M , and 10 −6 M BQ‐123 displaced 84 and 58% of ET binding to capillaries from tumors and brains, respectively. In addition, competition curves obtained in the presence of increasing concentrations of ET‐3 showed two components (IC 50 = 5.7 ± 2.5 × 10 −10 and 1.4 ± 0.2 × 10 −6 M for tumor microvessels, 1.8 ± 0.6 × 10 −10 and 1.1 ± 0.3 × 10 −6 M for brain microvessels, respectively). Our results indicate that (a) the method we used is simple and highly sensitive for detecting and characterizing various receptors in tumor capillaries, especially in the case of a sparse specimen, and (b) capillaries in glioblastomas express specific high‐affinity ET binding sites, candidates for biologically active ET receptors, which predominantly belong to the ET A subtype.