Expression of endothelin and ETB receptors in the megakaryoblastic MEG-01 cell line

The presence of endothelin (ET) receptors and the nature of the subtype and expression of ET were investigated in the human megakaryoblastic cell line MEG-01. By the RT-PCR procedure, we have shown that both ETA and ETB receptor subtype mRNAs are expressed in the cells. However, binding experiments have shown that the selective ETB receptor antagonist BQ788, but not the selective ETA receptor antagonist BQ123, competes with the specific binding of [125I]ET-1. Using immunocytochemistry, RIA, and RT-PCR Southern blot, we have shown that MEG-01 cells express ET-1. In addition, ET (1-21)-like immunoreactivity was released from the cells into the culture medium, and this release was modulated by thrombin. These data suggest that an ET-1-mediated autocrine loop could occur in the human megakaryoblastic MEG-01 cell line.