Differences in arachidonic acid metabolism and effects of aspirin between one- and two-kidney Goldblatt hypertensive rats

Aspirin and blood pressure: Effects when used alone or in combination with antihypertensive drugs

Arterial hypertension is a major risk factor for cardiovascular and renal events. Lowering blood pressure is thus an important strategy for reducing morbidity and mortality. Since low-dose aspirin is a cornerstone in the prevention of adverse cardiovascular outcomes, combined treatment with aspirin and antihypertensive drugs is very common. However, the impact of aspirin therapy on blood pressure control remains a subject of intense debate. Recent data suggest that the cardioprotective action of aspirin extends beyond its well-known antithrombotic effect. Aspirin has been shown to trigger the synthesis of specialized pro-resolving lipid mediators from arachidonic acid and omega-3 fatty acids. These novel anti-inflammatory and pro-resolving mediators actively stimulate the resolution of inflammation and tissue regeneration. Additionally, they may contribute to other protective effects on redox status and vascular reactivity that have also been attributed to aspirin. Of note, aspirin has been shown to improve vasodilation through cyclooxygenase-independent mechanisms. On the other hand, higher aspirin doses have been reported to exert a negative impact on blood pressure due to inhibition of cyclooxygenase-2 activity, which reduces renal blood flow, glomerular filtration rate and sodium and water excretion. This review aims to provide an overview of the effects of aspirin on blood pressure and the underlying mechanisms, focusing on the interaction between aspirin and antihypertensive drugs. Studies in both experimental and human hypertension are presented.

Aspirin lowers blood pressure in patients with renovascular hypertension

To clarify the role of renal prostanoid in hyperreninemia and high blood pressure in human renovascular hypertension, we measured prostaglandin E2 and renin activity in renal venous and abdominal aortic plasma before and after the intravenous administration of the cyclooxygenase inhibitor, aspirin DL-lysine. Subjects were six patients with unilateral renovascular hypertension and six with essential hypertension. In patients with renovascular hypertension, prostaglandin E2 concentration in renal venous plasma from the stenotic kidney was 9.25 +/- 1.48 pg/ml, which was significantly higher (p less than 0.01) than the concentration in the renal venous plasma from the normal kidney (4.97 +/- 1.02 pg/ml) or in the aortic plasma (2.59 +/- 0.15 pg/ml). Plasma renin activity was also higher in the renal vein of the stenotic kidney than in the other two sites. The stenotic side/normal side ratio of the renal venous prostaglandin E2 correlated significantly with a renin ratio greater than 1.5 (r = 0.8211, p less than 0.05). Intravenous injection of aspirin DL-lysine (18 mg/kg) 30 minutes later markedly suppressed prostaglandin E2 and renin levels at all sites and clearly lowered arterial blood pressure (mean: from 120 +/- 6 to 110 +/- 5 mm Hg, p less than 0.01). The reduction in blood pressure correlated significantly with the suppression of plasma renin activity in the aorta (p less than 0.05) and in the renal vein of the stenotic kidney (p less than 0.01). Conversely, in patients with essential hypertension, aspirin had little effect on renin levels and increased mean blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in prostanoid synthesis in response to diet and hypertension in one-kidney, one clip rats

This study was designed to examine the effects of diets that alter prostaglandin biosynthesis on the blood pressure in one-kidney, one clip rats with established hypertension and to compare the prostanoid generating capacity of hypertensive animals with those that remained normotensive. Rats attaining blood pressures of at least 180 mm Hg within 8 weeks of nephrectomy and renal artery stenosis were paired by weight and blood pressure and then placed on either a safflower oil or a prostaglandin I2 inhibitory diet (cod liver oil-linseed oil mix) for 4 weeks. Animals with blood pressures of less than 150 mm Hg were also paired for the same two dietary regimens. Comparison between the two blood pressure groups revealed that on both dietary regimens hypertensive rats produced significantly more aortic 6-keto-prostaglandin F1 alpha and serum thromboxane B2. Rats on the cod liver oil-linseed oil diet incorporated eicosapentaenoic acid into tissue stores with a corresponding decrease in arachidonic acid and significantly impaired ability to generate serum thromboxane B2 (36%), aortic 6-keto-prostaglandin F1 alpha (65%), renal homogenate 6-keto-prostaglandin F1 alpha (64%) and prostaglandin E2 (58%), and urinary prostaglandin E2 (70%) and 6-keto-prostaglandin F1 alpha (52%). Despite these differences in prostanoid synthesizing capacity, no differences in blood pressure were observed between the safflower oil-fed rats and rats fed cod liver oil-linseed oil within either the hypertensive or normotensive groups. These results suggest that prostanoids do not play a major role in maintaining blood pressure in established one-kidney, one clip hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)