The Hypotensive Effect of Docosahexaenoic Acid Is Associated with the Enhanced Release of ATP from the Caudal Artery of Aged Rats

Manuscript received 15 July 1998. Initial reviews completed 13 August 1998. Revision accepted 19 October 1998.

Michio Hashimoto, Kazumasa Shinozuka^*, Shuji Gamoh, Yoko Tanabe, Md Shahdat Hossain, Young Mi Kwon^*, Noriaki Hata, Yoshihisa Misawa, Masaru Kunitomo^*, and Sumio Masumura

Department of Physiology, Shimane Medical University, Izumo 693-8501, Japan; ^* Department of Pharmacology, Faculty of Pharmaceutical Science, Mukogawa Women's University, Koshien Kyuban-cho, Nishinomiya 663-8179, Japan; and  Applied Research Department, Harima Chemicals Incorporated, Tsukuba 300-2635, Japan

Fish oils have been shown to lower blood pressure in hypertensive subjects. To determine the mechanism of this hypotensive effect, we examined the effects of docosahexaenoic acid (DHA), one of the (n-3) polyunsaturated fatty acids in fish oil, on blood pressure and on the release of adenyl purines, such as ATP, ADP, AMP and adenosine, from the caudal arteries of aged rats. Aged female Wistar rats (100 wk) were fed a high cholesterol diet and were administered intragastrically ethyl all-cis-4,7,10,13,16,19-docosahexaenoate [300 mg/(kg·d)] for 12 wk (DHA group) or vehicle alone (control group). Compared with the controls, rats supplemented with DHA had significantly greater (10.1%) DHA concentrations in the caudal arteries. This was associated with more total (n-3) arterial fatty acids, a greater unsaturation index of arterial fatty acids, 43.9% lower plasma noradrenaline levels and the repression of the elevation in blood pressure observed with advancing age. The amount of purines released, both spontaneously and in response to noradrenaline, from arterial segments of DHA-supplemented rats was significantly higher than that released from tissues of control rats. Regression analysis revealed significant negative relationships between the total amount of purines released from the artery and the systolic (SBP) and diastolic (DBP) blood pressures. These results suggest that in aged rats, supplementation with DHA alters the membrane fatty acid composition as well as the amount of ATP released from vascular endothelial cells and decreases plasma noradrenaline, and that these factors may ameliorate the rise in blood pressure normally associated with advancing age.

The Journal of Nutrition Vol. 129 No. 1 January 1999, pp. 70-76
Copyright ©1999 by the American Society for Nutritional Sciences

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