Molecular forms of circulating atrial natriuretic peptides in human plasma and their metabolites

Abstract

High performance gel permeation chromatography (HP-GPC) followed by four radioimmunoassays (RIAs) devised to amino acids (a.a.) 1–30, 31–67, 79–98, and 99–126 of the 126 a.a. atrial natriuretic factor (ANF) prohormone revealed that the proANF(1–30) assay immunoreactivity in plasma is 50% proANF(1–30) and 50% proANF(1–98). The HP-GPC evaluation of plasma followed by proANF(31–67) and ANF [i.e., proANF(99–126)] assays revealed that proANF(31–67) and ANF circulate as distinct peptides. The HP-GPC plasma examination followed by proANF(79–98) assay immunologically recognized three peaks in plasma consistent with proANF(1–98), -(68–98), and -(79–98). Similar HP-GPC evaluation of urine followed by these RIAs indicated that the proANF(1–30), -(79–98), and ANF assays only recognize 500 mol.wt. or less peptides, and the proANF(31–67) RIA recognizes a nearly intact proANF(31–67) with only two to three amino acids removed during processing of this peptide.