Identification of endothelin receptors in various regions of rat brain.

Endothelins (ET) are a family of 21 amino acid peptides which carry a high degree of hemology. ET-1, originally isolated from porcine endothelium in culture, is an unusually potent vasoconstrictor. Recent studies indicated the presence of ET-1 and ET-3 in the CNS, and autoradiographic evidence supported the presence of specific ET-1 binding sites. The present study aimed to raise evidence in support for the presence of ET-1 and ET-3 receptors in the rat CNS, to establish their spatial distribution, and gain insight on the molecular species which could be associated to ET-1 and ET-3 binding. The data support the presence of specific binding sites for ET-1 and ET-3 and a heterogeneous distribution of these sites in the CNS. The highest densities were found in the cerebellum (greater than 2200 fmol-mg protein) and the lowest in the cerebral cortex (500 fmol/mg protein). Our data also suggest that ET-1 and ET-3 labelled two different proteins of 45 Kd and 37 Kd molecular weight, but no evidence for separate ET-1 and ET-3 receptors could be noted. These data provide further evidence in support for the possible role of ET-1 and ET-3 in neuromodulation/neurotransmission in the CNS.