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

Using radio-immunoassays for the C-terminal sequence of alpha-atrial natriuretic polypeptide [atrial natriuretic factor (ANF)-(99-126)], alpha-ANP (17-28) [ANF-(115-126)], which corresponds to gamma-human ANP [115-126; gamma-hANP-(115-126)] and for the N-terminal sequence of gamma-hANP [human ANF-(1-126)], gamma-hANP-(1-25) [human ANF-(1-25)], we detected the parallel distribution of alpha-hANP-like immunoreactivity and gamma-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 alpha-ANP revealed that gamma-ANP is synthesized in the brain and cleaved into N-terminally deleted form(s) of alpha-ANP and 10-K N-terminal fragment(s) of gamma-ANP, which coexist within the neuron. These results suggest that the post-translational processing of gamma-ANP in the brain is different from that in the heart.