Rat peritoneal macrophages express endothelin ET(B) but not endothelin ET(A) receptors

The properties of endothelin receptors on rat peritoneal macrophages were examined in in vitro receptor autoradiographic binding experiments and in a reverse transcription-polymerase chain reaction (RT-PCR) study. Dense and specific [ 125 I ]endothelin-1 binding sites were detected on the macrophages. [ 125 I ]Tyr13–Suc–[Glu9,Ala11,15]–endothelin-1(8-21), IRL1620, a selective endothelin ETB receptor ligand, but not [ 125 I ](N-[(hexahydro-1-azepinyl)carbonyl]) l -Leu(1-Me) d -Trp– d -Tyr, PD151242, a selective endothelin ETA receptor ligand, specifically bound to rat macrophages (Kd=0.75±0.19 nM, Bmax=7.77±2.50 fmol/mg). RT-PCR experiments also showed the expression of endothelin ETB receptor mRNA, but not endothelin ETA receptor mRNA, in these macrophages. These results indicate that rat peritoneal macrophages apparently express the endothelin ETB receptor but not the endothelin ETA receptor.