I-Angiotensin 1-7 binds to a different site than angiotensin 1-7 in tissue membrane preparations

Document Type

Article

Publication Date

5-1-2021

Publication Title

Endocrine

Keywords

Angiotensin 1–7, Iodoangiotensin 1–7, Metallopeptidases, Radioligand-binding assay

ISSN

1355-008X

Volume

72

Issue/No.

2

First Page

529

Last Page

538

Abstract

PURPOSE: To study the receptor for Angiotensin (Ang) 1-7 using a radioligand (I-Ang 1-7)-binding assay. For more than a decade, Mas has been viewed as the receptor for Ang 1-7; however, Ang 1-7 binding has not been pharmacologically characterized in tissue membrane preparations. METHODS: Radioligand-binding assays were carried out using tissue membrane preparations using radioiodinated Angiotensin 1-7 (I-Ang 1-7) to characterize its binding site. Non-radioactive I-Ang 1-7 was used to test if the addition of an iodine to the tyrosine moiety of Ang 1-7 changes the ability of Ang 1-7 to competitively inhibit I-Ang 1-7 binding. RESULTS: I-Ang 1-7 binds saturably, with moderately high affinity (10-20 nM) to a binding site in rat liver membranes that is displaceable by I-Ang 1-7 at nanomolar concentrations (IC = 62 nM) while Ang 1-7 displaces at micromolar concentrations (IC = 80 µM) at ~22 °C. This binding was also displaceable by inhibitors of metalloproteases at room temperature. This suggests that I-Ang 1-7 binds to MMPs and/or ADAMs as well as other liver membrane elements at ~ 22 °C. However, when I-Ang 1-7-binding assays were run at 0-4 °C, the same MMP inhibitors did not effectively compete for I-Ang 1-7. CONCLUSIONS: The addition of an iodine molecule to the tyrosine in position 4 of Ang 1-7 drastically changes the binding characteristics of this peptide making it unsuitable for characterization of Ang 1-7 receptors.

ORCID ID

0000-0002-6434-2138

DOI

10.1007/s12020-020-02572-2

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