The endothelin receptor profile in L6 myotubes

In this study we characterized the endothelin (ET) receptors of cultured L6 myotubes in order to gain a further insight into the mechanism of the ET effect on skeletal muscle cells. Displacements of ¹²⁵I-ET-1 by unlabeled ET-1, ET-2 and ET-3 revealed receptors with a high affinity (K(d) < 1 nmol/l) to ET-1 and ET-2 and a low affinity (K(d) > 100 nmol/l) to ET-3, which suggested the presence of primarily ET(A) receptors on L6 myotubes. These findings were complemented by displacement binding kinetics, in which the ET(A) receptor antagonist JKC-301 was used. Moreover, the ET-1-evoked increase in the cytosolic free Ca was blocked by JKC-301 but not by the ET(B) receptor antagonist IRL-1038. Collectively, these findings indicate that the ET-mediated response in cultured skeletal muscle cells is through the ET(A) receptor.