Comparison of binding characteristics of endothelin receptors on subpopulations of astrocytes.

Astrocytes in primary culture originating from different brain areas of the mouse embryo (striatum, cerebral cortex and mesencephalon) were compared for their [125I]-Endothelin-1 (ET-1) binding characteristics, in terms of affinity, binding capacity and specificity. Our results indicate that astrocytes from mesencephalon express about twice as many receptors as astrocytes from striatum or cortex (149,000 +/- 9700 vs 63,700 +/- 5600 and 81,900 +/- 5300, respectively), with similar affinities. Specificity patterns for the various peptides of the endothelins/sarafotoxins family (ET-1, -2, -3; SRTXa, b, c) are comparable in the three subpopulations of astrocytes: ET-1, -2 and SRTXb exhibit higher affinities than SRTXa and SRTXc. In addition, ET-3 and SRTXc seem to discriminate between different subsets of [125I]-ET-1 binding sites in the three subpopulations.