Characterization of Binding Sites for the Angiotensin II Antagonist 125I‐[Sarc1,Ile8]‐Angiotensin II on Murine Neuroblastoma N1E‐115 Cells

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Abstract
The murine neuroblastoma N1E-115 cell line contains binding sites for the angiotensin II (Ang II) receptor antagonist 125I-[Sarc1,Ile8]-Ang II (125I-SARILE). Binding of 125I-SARILE to N1E-115 membranes was rapid, reversible, and specific for Ang II-related peptides. The rank order potency of 125I-SARILE binding was the following: [Sar1]-Ang II = [Sar1Ile8]-Ang II > Ang II > Ang III = [Sarc1, Thr8]-Ang II > Ang I. Scatchard analysis of membranes prepared from confluent monolayers revealed a homogenous population of high affinity (KD= 383 ± 60 pM) binding sites with aBmax of 25.4 ± 1.6 fmol/mg of protein. Moreover, the density, but not the affinity, of the binding sites increased as the cells progressed from logarithmic to stationary growth in culture. Finally, agonist, but not antagonist, binding to N1E-115 cells was regulated by guanine nucleotides. Collectively, these results suggest that the murine neuroblastoma N1E-115 cell line may provide a useful model in which to investigate the signal transduction mechanisms utilized by neuronal Ang II receptors.