THE RECEPTORS FOR ENDOTHELINS AND THEIR ANALOGS IN SK-N-MC NEUROBLASTOMA-CELLS

The potency order of peptides to inhibit [I-125]endothelin-1 binding a nd to stimulate phosphatidylinositol phosphate (PtdInsP) turnover in S K-N-MC cells was consistent with the presence of ET(A)-endothelin rece ptors. Divalent cations enhanced [I-125]endothelin-1 binding by, in th e case of Mn2+, increasing radioligand affinity. Mn2+ did not induce c onformational changes in endothelin-1, and its effect was maintained i n solubilized receptors. Hence, metal ions may directly interact with endothelin receptors. The effects of BQ-123 and [Ala(1,3,11,15)]endoth elin-1 on PtdInsP turnover were investigated. Concentration-response c urves of endothelins were modeled by a second-order equation that assu mes pseudoirreversible ligand binding.