Hypotensive effect of fish protein hydrolysate

Fish protein hydrolysate (FPH) prepared from defatted sardine meal by treatment with alkaline protease was tested for inhibitory activity against angiotensin I converting enzyme (ACE) and for hypotensive effects on spontaneously hypertensive rats (SHR). FPH at 0.18mg protein/ml concentration provided 50% inhibition against ACE, and FPH was more effective compared with five hydrolysates prepared from defatted sardine meal by treatment with other proteases. Inhibitory activity was found in many fractions in gel chromatography of FPH, showing that FPH contained many kinds of active peptides. About 60% of the inhibitory activity of FPH was retained even after an in vitro digestivility test. When FPH was orally administered at a dosage of 2.0g protein/kg to SHR, blood pressure was reduced and the reduction continued for 6 hr after administration. Diet containing FPH as the sole protein source had a stronger hypotensive effect and a higher survival ratio in stroke-prone SHR (SHR-SP) than commercial diet. Furthermore, rats were examined histologically, but the incidence of abnormality in organs was not different from rats fed FPH and commercial diets.