Isosorbide
Isosorbide is an organic nitrate with vasodilator activity. Isosorbide relaxes vascular smooth muscle by formation of the free radical nitric oxide (NO), which is identical to the endothelium-derived relaxing factor (EDRF). NO activates guanylyl cyclase, thereby increasing the synthesis of cGMP within smooth muscle. Elevated cGMP levels in smooth muscle activate cGMP-dependent kinase activity that leads to release of sequestered Ca2+. In turn, free Ca+ triggers dephosphorylation of light chain myosin and relaxation of peripheral arteries and veins. In addition isosorbide relaxes coronary arteries, thereby increasing the blood circulation through the ischemic area.