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Magnesium causes nitric oxide independent coronary artery vasodilation in humans
H Teragawa1, M Kato, T Yamagata
1The First Department of Internal Medicine, Hiroshima University School of Medicine, 1-2-3 Kasumi, Minamiku, Hiroshima, Japan 734-8851. teragawa@mcai.med.hiroshima-u.ac.jp
Objective:
To determine how magnesium affects human coronary arteries and whether endothelium derived nitric oxide (EDNO) is involved in the coronary arterial response to magnesium.
Design:
Quantitative coronary angiography and Doppler flow velocity measurements were used to determine the effects of the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA) on magnesium induced dilation of the epicardial and resistance coronary arteries.
Setting:
Hiroshima University Hospital a tertiary cardiology centre.
Patients:
17 patients with angiographically normal coronary arteries.
Interventions:
Magnesium sulfate (MgSO(4)) (0.02 mmol/min and 0.2 mmol/min) was infused for two minutes into the left coronary ostium before and after intracoronary infusion of L-NMMA.
Main Outcome Measures:
Diameter of the proximal and distal segments of the epicardial coronary arteries and coronary blood flow.
Results:
At a dose of 0.02 mmol/min, MgSO(4) did not affect the coronary arteries. At a dose of 0.2 mmol/min, MgSO(4) caused coronary artery dilation (mean (SEM) proximal diameter 3.00 (0.09) to 3.11 (0.09) mm; distal 1.64 (0.06) to 1.77 (0.07) mm) and increased coronary blood flow (79.3 (7.5) to 101.4 (9.9) ml/min, p < 0.001 v baseline for all). MgSO(4) increased the changes in these parameters after the infusion of L-NMMA (p < 0.001 v baseline).
Conclusions:
Magnesium dilates both the epicardial and resistance coronary arteries in humans. Furthermore, the coronary arterial response to magnesium is dose dependent and independent of EDNO.