Endothelial cell function is proposed to be altered by a factor(s) in the maternal circulation of women with the pregnancy disorder preeclampsia. Our initial hypothesis was that in preeclampsia, such factor(s) would reduce synthesis of nitric oxide (NO) by endothelial cells. However, we previously observed increased NO synthase activity in endothelial cells exposed to plasma from preeclamptic women. This study tested whether exposing cells to plasma from preeclamptic women increased transcription and/or translation of endothelial NO synthase. Cultured bovine coronary microvascular endothelial cells were exposed to 2% plasma from patients with preeclampsia and patients with uncomplicated pregnancies. Nitrite production was greater in endothelial cells exposed to plasma from preeclamptic women (8.97 +/- 0.54 vs. 6.39 +/- 0.59 nmol nitrites.10(6) cells-1 x 24 h-1; P < 0.05). Similarly, endothelial NO synthase mass as measured by Western immunoblotting was significantly increased (20,980 +/- 1,406 vs. 15,047 +/- 1,003 absorbancy units; P < 0.02). There was no detectable difference in mRNA for endothelial NO synthase. However, actinomycin (3 micrograms/ml), a transcription inhibitor, significantly decreased nitrite production only in cells exposed to plasma from preeclamptic women (5.28 +/- 0.52 vs. 3.56 +/- 0.36 nmol.10(6) cells-1 x 24 h-1, P < 0.05). These findings indicate a regulation of the "constitutive" isoform of NO synthase by factor(s) in the blood of preeclamptic women, which may have significance in this pathological condition of pregnancy.