Regulatory peptides in the heart and major vessels of man and mammals

Studies on the distribution of peptides in human tissues have been made eit her by measuring responses to localized stimuli or by subjecting extracts o f different regions to radioimmunoassay (RIA). Attempts at isolating regula tory peptides from the mammalian tissues have resulted in the isolation of many bioactive fragments. Later, modification of initial isolation methods led to the identification of the native molecules in Various tissues and bo dy fluids. The present study examined atrial natriuretic peptide (ANP) and several other peptides in cardiac tissues of several species of laboratory mammal and human beings; using a sensitive and highly specific radioimmunoa ssays. In all the species studied, ANP-like immunoreactivity appeared to be highes t in the heart tissue of rat. The peptide was highest in the right atrium ( RA);of rat and lowest in the RA of guinea pig (P < 0.002). Neuropeptide Y ( NPY) another abundant cardiac peptide was present in the cardiac tissues of all species but was more in the left atrium (LA) than the RA of all specie s (P < 0.05). Calcitonin gene-related peptide (CGRP) was present throughout the cardiovascular system of the rat and guinea pig. Small but detectable amount of Neurotensin (NT) immunoreactivity was found in the rat but was co nsistently negative in the guinea pig cardiac tissues (P < 0.05). Substance P (SP) immunoreactivity was detected in the rat and higher quantities bein g in the Aorta but no trace of the peptide was detected in the left ventric le, aorta nor the pulmonary vein of post motem human. Though the structure of most of the species studied has been elucidated, th e primary structure of guinea pig ANP has not been fully generated. Thus th e data obtained may suggest that in keeping with these mammalian peptides, the primary structures may be variant. With most of the peptides studied (e .g. ANP, Neuropepdide Y), immunoreactivity occurs predominantly in the atri al tissues, but is also present in vessels outside the heart, a finding whi ch may be of functional significance.