CHANGE OF ENDOTHELIN RECEPTOR SUBTYPE IN THE MEG-01 HUMAN MEGAKARYOBLASTIC CELL-LINE

The aim of this investigation was to determine whether the endothelin receptor subtype of a megakaryoblastic cell line (MEG-01) changes duri ng culture passages as cells undergo maturation and differentiation. O n early-passage cells, binding of [I-125]endothelin-1 was completely i nhibited by 1 mu M BQ 123 [D-tryptophanyl-D-aspartl-prolyl-D-valyl-leu cyl]), but not by sarafotoxin 6C. Also the endothelin-1-enhancing effe ct on [Ca2+](i) was prevented by BQ 123, whereas sarafotoxin 6C had no effect on [Ca2+](i). In late-passage sells, endothelin ETB analogs, u nlike endothelin ETA analogs, competed with binding of [I-125]endothel in-1. Endothelin ETB receptor agonists increased [Ca2+](i) while the e ndothelin-1-induced response was inhibited by BQ 788 a-(methoxycarbony l)-D-tryptophanyl]-D-norleucine), but not by BQ 123, although both end othelin ETA and ETB receptor mRNAs were expressed, as shown by reverse transcriptase-polymerase chain reaction. These results demonstrate th at in MEG-01 cells switch from expression of endothelin ETA to express ion of ETB receptors during culture. The data also suggest that late-p assage MEG-01 cells look like platelets, in terms of endothelin recept or subtype. (C) 1998 Elsevier Science B.V.