Fig. 4.

Vascular effects of magnesium sulphate [66]. Magnesium is a potent vasodilator of uterine and mesenteric arteries as well as the aorta, but has little effect on cerebral arteries. In vascular smooth muscle, magnesium competes with calcium for binding sites, in this case for voltage-operated calcium channels (VOCC). Decreased calcium channel activity lowers intracellular calcium, resulting in relaxation and vasodilation. In the endothelium, magnesium increases production of prostaglandin I₂ which in turn decreases platelet aggregation. Magnesium also increases NO production causing vasodilation. From Euser and Cipolla [66], with permission, adapted.