Atrial natriuretic factor in rat hypothalamus, atria and plasma: determination by specific radioimmunoassay.

A rapid and reproducible radioimmunoassay method was developed for rat atrial natriuretic factor (ANF)-IV. The method is also applicable to human atrial peptide. ANF was detected in rat hypothalamus (5.03 pmoles/g tissue), right (86.8 pmoles/mg tissue) and left atria (52.5 pmoles/mg tissue), and plasma (156 fmoles/ml). After high salt intake immunoreactive ANF in atria and plasma increased significantly, while a significant decrease was observed in hypothalamus. Gel chromatography revealed high and low molecular weight ANF in atria and hypothalamus while only a low molecular weight form was found in plasma.