Journal
JOURNAL OF HYPERTENSION
Volume 26, Issue 7, Pages 1453-1462Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1097/HJH.0b013e328300a232
Keywords
aldosterone; angiotensin II; cardiac function; mineralocorticoid receptor; oxidative stress; sodium
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Background Salt status plays a pivotal role in angiotensin-II- induced organ damage by regulating reactive oxygen species status, and it is reported that reactive oxygen species activate mineralocorticoid receptors. Method To clarify the role of reactive oxygen species-related mineralocorticoid receptor activation in angiotensin-II- induced cardiac dysfunction, we examined the effect of the following: salt status; an MR antagonist, eplerenone; and an antioxidant, tempol in angiotensin-II-loaded Sprague Dawley rats. Results Angiotensin-II/salt-loading elevated blood pressure, and neither eplerenone nor tempol antagonized the rise in blood pressure significantly. Left ventricular diastolic function was monitored by measuring peak velocity of a mitral early inflow (E), the ratio of mitral early inflow to atrial contraction related flow (E/A), deceleration time of mitral early inflow and -dP/dt, the time constant (T), and filling pressure (left ventricular end-diastolic pressure) by echocardiography or cardiac catheterization. Despite the suppressed serum aldosterone, left ventricular diastolic function was deteriorated with angiotensin II/high salt, but not affected by angiotensin II/low salt. However, angiotensin-II/salt-induced cardiac dysfunction was restored by eplerenone and tempol. Nicotinamide adenine dinucleotide phosphateoxidase-derived superoxide formation was greater in the hearts of the angiotensin II/high-salt rats than of the angiotensin II/low-salt rats. The expression of the Na+ -H+ exchanger isoform 1, a target of mineralocorticoid receptor activation, was significantly increased in the angiotensin II/high-salt group.Both tempol and eplerenone inhibited the angiotensin-II/salt-induced upregulation of Na+ -H+ exchanger isoform 1. Conclusion These findings demonstrate that mineralocorticoid receptor activation by oxidative stress can cause left ventricular diastolic dysfunction in a rat model of mild hypertension.
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