MACROMOLECULAR FORMS OF ATRIAL-NATRIURETIC-FACTOR IN HUMAN PLASMA

Identification of atrial natriuretic factor (ANF) in the mammalian hea rt demonstrates that the heart is an endocrine organ. Radioimmunoassay combined with chromatographic separation has revealed different molec ular forms of ANF circulating in plasma, including a macromolecular fo rm referred to as ''big ANF'' The present study was undertaken to puri fy and characterize this circulating form in human blood. The chromato graphic behaviour of the ANF in the fractionation of human plasma on A ffi-Gel Blue under different conditions of ionic strength has been des cribed. All the fractions collected were analyzed by SDS-PAGE. Measure ment of ANF was carried out by RIA. Immunoblot analysis with eluant bu ffers of the highest and lowest ionic strengths showed the presence re spectively of an immunoreactive band with a molecular weight of approx imately 89 kd and of an immunoreactive region in the range of molecula r weight higher than 116 kd. These data suggest that at least two plas ma proteins may function as carriers of ANF.