Peptides derived from atrial natriuretic polypeptide precursor in human and monkey brains

Using radio-immunoassays for the C-terminai sequence of a-atrial natriuretic polypeptide [atrial natriuretic factor (ANF)-(99-126)], α-ANP (17-28) [ANF-(115-126)], which corresponds to γ-human ANP [115-126; - γ -hAN P-(115-126)] and for the N-terminal sequence of γ -hANP [human ANF-(1-126)], γ -hANP-(1-25) [human ANF-(1-25)], we detected the parallel distribution of α-hANP-like immunoreactivity and - γ -hANP-(1- 25)-like immunoreactivity in the human and monkey brains, with the highest concentrations in the midbrain and the pons. High performance gel permeation chromatography coupled with the two radio-immunoassays and also with another radio-immunoassay using a monoclonal antibody against the N-terminal sequence of a-ANP revealed that γ -ANP is synthesized in the brain and cleaved into N-terminally deleted form(s) of α-ANP and 10-K N-terminal fragment(s) of γ -ANP, which coexist within the neuron. These results suggest that the post-translational processing of γ -ANP in the brain is different from that in the heart.