Identification of the released form of atrial natriuretic factor by the perfused rat heart

Atrial natriuretic factor (ANF), released by the isolated perfused rat heart, was extracted from the perfusates by C18 Sep-Pak cartridges and then isolated by immunoaffinity chromatography and by reverse phase HPLC. About 500 ng of immunoreactive material were so obtained and submitted to amino acid sequencing. The C-terminal Tyr was detected by radiolabelling. Identification of these residues indicated that the primary structure corresponds to ANF (Ser 99-Tyr 126) which is identical to the circulating form in the rat. These results indicate that the ANF released by the atria corresponds to a short peptide. Therefore, its maturation process may therefore take place either intracellularly or during secretion and implicates a tryptic-like cleavage after a single Arg residue in position 98.