Identification of Endothelin Receptor Subtype (ETB) in Human Cerebral Cortex Using Subtype-Selective Ligands |
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Authors: | Raquel Fernández-Durango José A de Juan Horatio Zimman Francisco J Moya Mario Garcia de la Coba Arturo Fernández-Cruz |
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Institution: | Centro de Diabetes e Hipertensión, Hospital Universitario San Carlos, Madrid, Spain |
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Abstract: | Abstract: Specific endothelin (ET) binding sites were characterized in membranes prepared from human cerebral cortices using binding assay and cross-linking analysis. The presence of immunoreactive (IR) ET-1 was studied by radioimmunoassay. Saturation binding experiments revealed that the K D and B max for 125I-ET-1 and 125l-ET-3 to membranes from gray matter were 25 ± 6 pM and 115 ± 15 fmol/mg of protein and 24 ± 5 p M and 108 ± 13 fmol/mg of protein, respectively. Similar results were obtained for white matter. In the presence of 10 n M sarafotoxin-6c, which is selective for ETB receptors, 125I-ET-1 and 125l-ET-3 binding was totally abolished. However, in the presence of 1 μ M BQ123, which is selective for ETAreceptors, both bindings were not affected. These results suggest that the human cerebral cortex contains only ETBreceptors. Cross-linking of 125I-ET-1 and 125l-ET-3 to membranes with disuccinimidyl suberate resulted in the labeling of two bands of 48 and 31 kDa. Concentrations of IR-ET-1 in the gray and white matter were 7.0 ± 3.2 and 2.5 ± 1.7 fmol/g wet weight, respectively. The demonstration of high-affinity ETB receptors and the presence of IRET-1 suggest that the peptide may act as a neurotransmitter or neuromodulator in the human cerebral cortex. |
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Keywords: | Endothelin ETB receptors Human cerebral cortex Subtype-specific ligand binding |
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