Synonyms: Atriopeptin-21(rat),1-de-L-serine-2-de-L-serine-6-L-serine-17-L-methionine-20-glycine-21-L-arginine-21a-L-arginine-21b-L-phenylalanine-;1,2-Dithia-5,8,11,14,17,20,23,26,29,32,35,38,41,44,47,50-hexadecaazacyclotripentacontane,cyclic peptide deriv.; Atrial natriuretic peptide-21 (frog); Atriopeptin-21(frog); Frog atrial natriuretic factor 21