SUPPRESSIVE ACTION OF DOCOSAHEXAENOIC ACID ENRICHED-EUGLENA ON REDUCTION OF ENDOTHELIUM-DEPENDENT RELAXATION IN STROKE-PRONE SPONTANEOUSLY HYPERTENSIVE RATS (SHRSP)

Stroke-prone spontaneously hypertensive rats (SHRSP) were fed a diet c ontaining docosahexaenoic acid (DHA)-enriched Euglena glacilis (DHA-Eu glena) as the protein source from 5 weeks of age. The effects on endot helial functions were investigated by perfusion experimentation using mesenteric vasculature, and compared with the effects of antihypertens ive drugs. (1) At 13 weeks of age, SHRSP fed the DHA-Euglena diet show ed an average blood pressure of 220 mmHg, which was 20 mmHg lower (p<0 .05) than that in the control group, while SHRSP of the captopril-trea ted group (angiotensin I converting enzyme inhibitor: 200 mg/L drinkin g water) and hydralazine-treated group (vasodilator: 60 mg/L drinking water) showed marked hypotensive effects with blood pressures of 150-1 60 mmHg and 180-190 mmHg, respectively. (2) The constriction response to norepinephrine (NE) was lower (p<0.01) in the mesenteric vasculatur e isolated from the DHA-Euglena-treated SHRSP than in that from the co ntrol group. (3) When the mesenteric vasculature isolated from 13-week -old SHRSP fed the DHA-Euglena diet was perfused with an acetylcholine solution (10(-6) M) in the presence of NE (8 x 10(-6) M), the relaxat ion rate was 81%, which was higher (p<0.01) than that in the control g roup (61%). Among the antihypertensive-treated groups, the captopril-t reated group gave nearly the same relaxation rate as the DHA-Euglena d iet group, while the hydralazine-treated group indicated a slightly lo wer rate (65%). At 18 weeks of age, the endothelium-dependent relaxati on of SHRSP in the control group was further reduced (28%), but in bot h the DHA-Euglena diet group and antihypertensive-treated groups, the relaxation rates were not substantially different from the levels at 1 3 weeks of age. Reduction of the endothelium function in SHRSP occurs due to aging and blood pressure elevation. However, by improving nutri tional conditions by the feeding of a DHA-Euglena diet, the endothelia l functions were protected without a fall in blood pressure unlike ant ihypertensive drugs. It is hence considered that nutritional improveme nt helps maintain a sound architecture for the vascular wall, thereby leading to the suppression and delay of onset of cerebrovascular disea ses, and subsequently to the prolongation of life-span.