Atrial extracts contain factors which induce potent natriuresis 1,2 changes in renal haemodynamics3, and relax pre-contracted vascular smooth muscle3-5. Low-molecular-weight peptides which mimic these actions have now been purified by several groups 1,2,6-12, including ours (see accompanying paper9), and higher-molecular-weight proteins with similar but less potent biological activities have also been identified and are presumed to be precursors 6,7,9-12. If released into the circulation, these peptides, collectively called atrial natriuretic factor (ANF), may play a significant part in blood-pressure homeostasis, regulation of extracellular fluid volume and as antagonists to the hypertensive effects of the reninangiotensin system and other hormonal and neurotransmitter systems. We describe here the isolation and characterization of rat atrial cDNA clones which encode ANF. Nucleotide sequence analysis shows that auriculin9 corresponds to the 25 amino acids located close to the C-terminus of a 152-amino acid ANF precursor. Analysis of the in vitro translation products of precursor ANF mRNA suggests that multiple forms of the precursor may exist.
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