Lowering Systolic Blood Pressure and Increases in Vasodilator Levels in SHR with Oral .ALPHA.-Linolenic Acid Administration

Abstract

The present study attempted to clarify the antihypertensive effect and its mechanism when alpha-linolenic acid (ALA) is administered orally. For this purpose, 1 mL of flaxseed oil, which is rich in ALA, and high oleic safflower oil was administered orally to spontaneously hypertensive rats (SHR) of a control and an ALA group on days 1 and 5. Systolic blood pressure was measured on day 1, and blood and liver were collected on day 5. Four hours after the oral administration on day 1, systolic blood pressure of the ALA group was lower than that of the control group. Levels of plasma vasodilators, such as prostaglandin I(2) metabolite, nitric oxide metabolites, and bradykinin, in the ALA group were significantly higher than those in the control group, but levels of vasoconstrictors, such as angiotensin II and thromboxane A(2) metabolite, did not differ significantly. It is known that bradykinin induces prostaglandin I(2) and nitric oxide. The present study shows that ALA reduced the systolic blood pressure of SHR, and its mechanism may be related to increases of prostaglandin I(2) and nitric oxide through bradykinin stimulation.

Dietary Alpha-Linolenic Acid Inhibits Angiotensin-Converting Enzyme Activity and mRNA Expression Levels in the Aorta of Spontaneously Hypertensive Rats

“…The experimental plan was approved by the Laboratory Animal Care Committee of the Research Laboratory, The Nisshin OilliO Group, Ltd. The temperature of the animal room was set at 23 1 , with RH of 50 5% and illumination from 0800 to 2000 h. The animals were also allowed free access to an experimental diet containing 10% high-oleic safflower oil (HOSO, The Nisshin OilliO Group, Ltd., Tokyo, Japan) before the experiment. Male SHR of the Izumo colony (SHR/Izm, Japan SLC, Inc., Hamamatsu, Shizuoka, Japan) were individually housed in stainless steel wire cages and allowed free access to sterilized water.…”

Interaction between .ALPHA.-Linolenic Acid-Enriched Oil and ACE Inhibitor Concerning the Decrease in Blood Pressure in SHR

“…Sekine et al 9) administered ALA to SHR and observed increases in the circulating bradykinin, PGI 2 metabolite, and NO metabolite levels. These results suggest that increases in vasodilators via bradykinin are involved in the depressor effect of ALA. Angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II with a marked pressor activity.…”

“…a-Linolenic acid (ALA) has been shown by animal [1][2][3][4][5][6][7][8][9] and epidemiological studies 10,11) to exhibit an antihypertensive effect. Blood pressure was reported to have been significantly lower in SHR administered ALA than in the controls 9) .…”

“…ACEI decreases the blood pressure by reducing the pressor factor and increasing the depressor factor. ALA has also been reported to reduce the blood pressure by increasing the circulating bradykinin concentration 9) . Therefore, the blood pressure may be reduced further by the simultaneous intake of ALA and ACEI.…”

“…Blood pressure was reported to have been significantly lower in SHR administered ALA than in the controls 9) . Epidemiological studies have shown a negative correlation between ALA intake and blood pressure 10,11) .…”