PURPOSE: To provide the titled agent containing a blood pressure suppressing fraction obtained from the cultivation product of microorganisms belonging to the pertussis phase-I bacteria or phase-II bacteria, as an active component.

CONSTITUTION: The objective agent contains as an active component, a biologically active fraction produced by bacteria belonging to Bordetella genus. The fraction is a blood pressure suppressing fraction separated from the culturing medium obtained by culturing bacteria belonging to pertussis phase I bacteria or phase-II bacteria which are known as pathogenic bacteria. The active fraction has the following characteristics: molecular weight, 77,000±6,400 by gel filtration; protein content, ≥95wt% by Lowry process; glucide content, about 1wt% by sulfuric acid process; the amino acid composition and amounts (μM/100μM) in the protein component, as shown in the figure; electrophoresis, a sharp, single band to the cathode side in polyacrylamide gel.