THE ROLE OF NITRIC-OXIDE, ENDOTHELIN, AND PROSTAGLANDINS IN THE TRANSITION OF THE PULMONARY CIRCULATION

The pulmonary endothelial cell regulates fetal and transitional pulmon ary vascular resistance by producing and releasing locally acting vaso dilating and vasoconstricting mediators. Nitric oxide, endothelin, and the eicosanoids are three endothelial-derived products that play very important roles in effecting change from the high resistance, low flo w pulmonary circulation in utero to the low resistance, high flow pulm onary circulation postnatally. This article reviews the roles of these three mediators in the fetal and transitional circulations. Understan ding the mechanisms by which these mediators influence vascular tone a llows for a more rational approach to disease states associated with a bnormal postnatal adaptation of the pulmonary circulation.