Nitric oxide in normal and preeclamptic pregnancy.

Nitric oxide (NO) is a key molecule involved in a variety of biological functions throughout the whole body. Many studies have been devoted to establish the role of NO in perinatal medicine and the different findings have promoted the clinical use of NO donors as new pharmacological tools. NO regulates the vascular tone and blood flow by activating soluble guanylate cyclase in the vascular smooth muscles. NO is essential for leukocyte adhesion and platelet aggregation, and it controls mitochondrial oxygen consumption. Abnormalities in vascular NO production and transport result in endothelial dysfunction with various cardiovascular disorders such as hypertension, atherosclerosis and angiogenesis-associated disorders. The NO system has important roles in mammalian reproductive physiology, especially in the utero-placental system. It has been shown to participate in the extravillous trophoblast invasion of decidua and myometrium, in regulation of vascular reactivity of utero-placental and fetal-placental circulations, in prevention of platelet and neutrophil aggregation and adhesion in the intervillous space, and in trophoblast apoptosis. The aim of this review is to present the theoretical background and significance of NO in normal and preeclamptic pregnancy as well as to consider how NO donors could be useful in clinical practice.