Release of fatty acids by perfused vascular tissue in normotensive and hypertensive rats.

Abstract

SUMMARY The release of fatty acids from perfused mesenteries of spontaneously hypertensive rats (SHR) and control Wistar-Kyoto rats (WKY) was studied. The release of the prostaglandin precursors dihomogammalinolenic acid, arachidonte acid, and ekosapentaenoic acid was reduced in SHR when compared with age-matched WKY. The release of all other fatty acids detected in the effluent was also reduced. The differences in fatty add release were evident even when tissue levels of the fatty acids were similar or higher in SHR than in controls. The addition of evening primrose oil and fish oil into the diet partially corrected these defects. Evening primrose oil and fish oil both attentuated increases in blood pressure, but fish oil was more potent than primrose oil. Although both diets reduced vascular reactivity, primrose oil was more effective with lower doses of norepinephrine whereas fish oil blunted the effects of both low and high doses of norepinephrine. added to the diet attenuate the development of hypertension or lower blood pressure in both animals and humans. '-' 4 The mechanism of the hypotensive effect is not well understood, although it is commonly believed to result from alterations in arachidonate-derived cyclooxygenase metabolites. However, both n-6 and n-3 fatty acids lower blood pressure, although their effects on prostaglandin synthesis are dissimilar. The fatty acids themselves alter membrane fluidity and blood viscosity and may have effects on blood pressure that are independent of their conversion to prostaglandins.The effect of diets rich in n-6 fatty acids in rats is generally an increase in tissue arachidonic acid (AA) and its conversion to cyclooxygenase metabolites.8 -I5 In contrast, diets rich in n-3 fatty acids are associated with a decrease in AA and a decrease in the synthesis of its metabolites.8 -l5 -' 7 These opposing observations cast doubt on the relevance of AA and its metabolites in the beneficial effects of PUFAs.Dihomogammalinolenic acid (DGLA) is worthy of further consideration. It gives rise to metabolites that are hypotensive and antiaggregatory and that

Changes in tissue polyunsaturated fatty acids with age, in spontaneously hypertensive rats

“…Although the proportion of AA in the mesenteric vessels of SHR is lower than in controls (34), the fraction of AA in the SHR aorta is higher than in controls at 1 and 3 mon. These results are similar to those for the kidney and indicate that the SHR aorta has the potential to synthesize more cyclooxygenase products than the aorta of age-matched WKY or may undergo changes in the incorporation of PUFA in the sn-2 position of membrane phospholipids.…”

High Fish Oil Diet Increases Oxidative Stress Potential in Mammary Gland of Spontaneously Hypertensive Rats

“…In another study (Bayorh et al 1989) chronic administration of eicosapentaenoic acid subcutaneously for 8 weeks lowered blood pressure in SHR significantly compared to WKY rats. In male SHR, some find that blood pressure decreases after supplementation with fish oil (high w-3; Hoffmann et al Von Au et al 1988;Brandle & Jacob 1990), dietary borage oil (Engler et al 1992;Engler 1993) or corn oil (high w-6; Mtabaji et al 1988).…”

“…Overall, the effects of high PUFA intakes on blood pressure remain controversial in human studies as well as in animal models. Increased dietary PUFA have been reported by some investigators to decrease blood pressure in spontaneously hypertensive rats (SHR; Hoffmann et al 1986;Mtabaji et al 1988;Von Au et al 1988;Bayorh et al 1989;Karanja et al 1989;Brandle & Jacob, 1990;Yin et al 1990;Engler et al 1992); however, others find no significant effects or actual increases in blood pressure (McGreger et al 1981;Codde et al 1989;Croft et al 1988;Kingsley & Snyder 1988;Watanabe et al 1989). Since hypertension is one of the risk factors for developing coronary heart disease, many people are motivated to increase dietary PUFA to achieve the cardiovascular beneficial effects.…”

“…The effects of dietary lipid intake on the blood pressure have been studied by several groups in male SHR (Hoffmann et al 1986;Mtabaji et al 1988;Yin et al 1990;Engler et al 1992), but there are no data available in the literature concerning similar effects in female SHR. All work concerning the effects of high PUFA diets in mammary tumour models has obviously been conducted in female rats, but female rats of the SHR strain have not been previously used as a laboratory model to study mammary tumour promotion.…”

Effect of Dietary Alpha-Linolenic Acid on Vascular Reactivity in Aorta of Spontaneously Hypertensive Rats

“…Sunano et al showed that endothelial dysfunction was profoundly involved in the development of hypertension 5) . Studies of animals and humans with hypertension have shown that dietary fish oil rich in n-3 polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) has a blood pressure-lowering effect [6][7][8][9] . Data from clinical trials have consistently shown that fish oil supplements can improve endothelial function [10][11][12][13] .…”