MACROMOLECULAR FORMS OF ATRIAL-NATRIURETIC-FACTOR IN HUMAN PLASMA

Identification of atrial natriuretic factor (ANF) in the mammalian heart demonstrates that the heart is an endocrine organ. Radioimmunoassay combined with chromatographic separation has revealed different molecular forms of ANF circulating in plasma, including a macromolecular form referred to as ''big ANF'' The present study was undertaken to purify and characterize this circulating form in human blood. The chromatographic behaviour of the ANF in the fractionation of human plasma on Affi-Gel Blue under different conditions of ionic strength has been described. All the fractions collected were analyzed by SDS-PAGE. Measurement of ANF was carried out by RIA. Immunoblot analysis with eluant buffers of the highest and lowest ionic strengths showed the presence respectively of an immunoreactive band with a molecular weight of approximately 89 kd and of an immunoreactive region in the range of molecular weight higher than 116 kd. These data suggest that at least two plasma proteins may function as carriers of ANF.