Environmental upregulation of the atrial natriuretic peptide gene in the living fossil, Limulus polyphemus

Northern blot analysis revealed that atrial natriuretic peptide (ANP) gene expression occurs in heart, hematocytes and gills of the invertebrate Limul us polyphemus, the horseshoe crab. In low salinity and on land ANP prohormo ne messenger RNA in Limulus' heart was 32-fold less compared to that in a v ertebrate heart (i.e., rat, Rattus norvegicus). ANP gene expression doubled (P < 0.05) in Limulus' heart and gills with change from land and low salin ity to medium salinity and osmolality. ANP gene expression was 10-fold high er in Limulus' gills in seawater (i.e., high salinity). The products of thi s ANP gene expression (i.e., ANP, long acting natriuretic peptide, vessel d ilator and kaliuretic peptide) were released and increased in the circulati on, i.e., hemolymph, of Limulus proportional to the increase in salinity an d osmolality (P = <0.01). These results suggest that modification of ANP ge ne expression enables animals to adapt to freshwater, seawater, and land. ( C) 1999 Academic Press.