Pregnancy-induced hypertension (PIH) is a relatively frequent disease in nulliparous, socioeconomically deprived black women seen in inner-city medical centers. Although the etiology of PIH may be multifactorial, when compared to control pregnancies, enhanced maternal vascular reactivity is a consistent finding. Further, increased utero-placental vascular resistance appears to be a good predictor, and perhaps an important factor for the development of pre-eclampsia. Enhanced vascular reactivity may be related to alterations in circulating vasodilators/pressors or, more likely, to changes in intrinsic myogenic tone. In the past several years it has become increasingly clear that hypertensive states with enhanced vascular reactivities are associated with altered states of cellular cation metabolism. Indeed, abnormal cellular cation metabolism, particularly decreased cation transport, is generally seen in the black hypertensive population. Clinicians and researchers alike have long recognized the importance of early non-invasive diagnosis of PIH and a better understanding of the physiological process behind the changes seen. Through our proposal, we hope to gain insight into both of these areas. In our proposed studies we will characterize gestational age-specific changes in cellular cation metabolism, circulating mediators of cation transport and peripheral vascular resistance in nulliparous black women, ages 15 to 25 years. We are particularly interested in the relationship between alterations in intracellular divalent cations (calcium and magnesium) and changes in maternal and umbilical vascular reactivity. Calcium, magnesium, sodium and potassium concentrations, and calcium, magnesium and sodium/potassium transport activity will be evaluated in maternal erythrocytes and platelets, fetal erythrocytes, umbilical artery smooth muscle cells, and placental membrane preparations. We hope to determine if alterations in cellular cation levels precede as well as related to he development of PIH and accompanying maternal-fetal complications. If this is indeed the case, it will offer the possibility of a relatively non-invasive early predictor for risk of pre-eclampsia.