Reduced uterine perfusion pressure during pregnancy in the rat is associated with increases in arterial pressure and changes in renal nitric oxide

A reduction in nitric oxide (NO) synthesis has been suggested to play a role in pregnancy-induced hypertension. We have recently reported that normal pregnancy in the rat is associated with significant increases in whole-body NO production and renal protein expression of neuronal and inducible NO synthase. The purpose of this study was to determine whether whole-body and renal NO production is reduced in a rat model of pregnancy-induced hypertension produced by chronically reducing uterine perfusion pressure starting at day 14 of gestation. Chronic reductions in uterine perfusion pressure resulted in increases in arterial pressure of 20 to 25 mm Hg, decreases in renal plasma flow (< 23%) and glomerular filtration rare (< 40%), but no difference in urinary nitrite/nitrate excretion relative to control pregnant rats. In contrast, reductions in uterine perfusion pressure in virgin rats resulted in no significant effects on arterial pressure. Renal endothelial (<4%) and inducible (< 11%) NO synthase protein expression did not decrease significantly in the chronically reduced uterine perfusion pressure rats relative to normal pregnant rats; however, significant reductions in neuronal NO synthase were observed (< 30%). The results of this study indicate that the reduction in renal hemodynamics and the increase in arterial pressure observed in response to chronic decreases in uterine perfusion pressure in pregnant rats are associated with no change in whole-body NO production and a decrease in renal protein expression of neuronal NO synthase.