Ethanol precipitate (HW-50) from hot water extract of lyophylized antarctic krill, Euphausia superba, was found to have gastric secretion inhibitory activity. Chemical analysis revealed that HW-50 contains a large amount of nucleic acids. By use of Sodium dodecylsulfate-phenol method, the nucleic acids were extracted from HW-50. The crude NA-fraction thus obtained contained 67.5% deoxyribonucleic acid, 29.5%, ribonucleic acid and 2.0% protein. The intraperitoneal administration of the NA-fraction caused a signifi. cant inhibition of gastric juice secretion in pylorus-ligated rats at a dose of 10 mg/kg (i.p.). The fraction was digested either with DNase or RNase, followed by the measurement of the biological activity. As a result, it was demonstrated that DNase-treated NA-fractions maintained gastric secretion inhibitory activity.
