Pregnancy-induced hypertension and preeclampsia remain leading causes of fetal and maternal morbidity and mortality, occurring in as many as 10% of pregnancies in the United States. They are a particular problem in first and adolescent pregnancies. The proposed study will investigate relationships during pregnancy among five factors: blood pressure, temporal changes in blood lead, dietary calcium intake, current lead ingestion, and bone lead mobilization. Rats will be exposed to lead prior to pregnancy, during pregnancy, or at both times, and will be fed a diet containing a low or normal concentration of calcium during pregnancy. Control groups of pregnant rats will not be exposed to lead and non-pregnant animals will also be studied. Variables to be measured include systolic blood pressure, blood and bone lead concentrations, and serum concentrations of parathormone, osteocalcin, and 25 and 1,25 dihydroxyvitamin D. The study will allow determination of whether the natural rise in blood lead late in pregnancy contributes to pregnancy-induced hypertension. It will also permit assessment of the relative effects of current lead exposure versus bone lead mobilization on blood lead and blood pressure during pregnancy. These studies will focus on quantifying blood lead/blood pressure relationships in the rat and investigation of factors that may influence this relationship during pregnancy. The concept that calcium supplementation is beneficial during pregnancy is not new. However, the proposed studies utilize lead exposure as a way to study if the mechanism of prevention of increases in blood pressure by dietary calcium during pregnancy is by suppression of lead absorption from the diet and/or suppression of bone lead mobilization. Thus, these studies may explain the variability of the results of other investigations that have assessed the independent effects of calcium and lead on blood pressure during pregnancy.
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