EXPRESSION OF ENDOTHELIN AND ET(B) RECEPTORS IN THE MEGAKARYOBLASTIC MEG-01 CELL-LINE

The presence of endothelin (ET) receptors and the nature of the subtyp e and expression of ET were investigated in the human megakaryoblastic cell line MEG-01. By the RT-PCR procedure, we have shown that both ET (A) and ET(B) receptor subtype mRNAs are expressed in the cells. Howev er, binding experiments have shown that the selective ET(B) receptor a ntagonist BQ788, but not the selective ET(A) receptor antagonist BQ123 , competes with the specific binding of [I-125]ET-1. Using immunocytoc hemistry, RIA, and RT-PCR Southern blot, we have shown that MEG-01 cel ls express ET-1. In addition, ET (1-21)-like immunoreactivity was rele ased from the cells into the culture medium, and this release was modu lated by thrombin. These data suggest that an ET-1-mediated autocrine loop could occur in the human megakaryoblastic MEG-01 cell line.