PRESENCE OF ATRIOPEPTIN-LIKE IMMUNOREACTIVITY IN HUMAN AND RAT MILK

Maternal milk is a significant source of hormones and other bioactive substances. They might be involved either in the control of mammary gl and function or in the regulation of growth and development of the neo nate. Atriopeptin (atrial natriuretic factor, ANF) is a peptide with s trong diuretic, natriuretic and vasorelaxant actions, and it has been suggested to play an important role in the circulatory adaptation to e xtrauterine life. The aim of this study was to determine whether ANF i s present in maternal milk, using radioimmunological analysis. The lev els of ANF-like substance in human milk were found to be in the range of 0.3-3.0 pg/ml, those in rat milk between 37-117 pg/ml. The measured concentrations of ANF were proportional to the volume of the extracte d milk. Serial dilutions of the extracts yielded curves which were not totally parallel to the human alpha-ANF standard curve. Our data indi cate that, during the first days after delivery, ANF levels in human m ilk are higher than those in later periods of lactation. This pilot st udy provides the first description of the presence of atriopeptin in m ilk. Though a detailed characterization of milk ANF-like immunoreactiv ity is needed, a biological significance of present findings seems pos sible.