L-arginine infusion reduces blood pressure in preeclamptic women through nitric oxide release

Objective: This study investigates the biochemical and cardiovascular effects of L-arginine administration in normotensive pregnant women and women with preeclampsia. Methods: The study groups consisted of 12 women with uncomplicated pregnancies and 17 preeclamptic patients, four of whom were on antihypertensive treatment. In both groups, saline infusion was started, followed by 30 g L-arginine administration, and finally more saline. Blood pressure was recorded every 5 minutes and blood samples were collected for measurement of serum citrulline, arginine, and nitrite levels. Amino acid assays were done by using high-performance liquid chromatography with fluorometric detection. Results: L-Arginine infusion was associated with a significant reduction of blood pressure in both groups, the decrease being greater in the women with preeclampsia. Baseline serum citrulline and arginine levels were not significantly different between the two groups. L-Citrulline levels were significantly increased during infusion of L-arginine, and the increase was significantly lower in the women with preeclampsia. Serum nitrite levels were increased only in controls and not in preeclampsia patients. The total citrulline production stimulated by L-arginine was related inversely to baseline blood pressure values and was unrelated to clinical parameters such as gestational age at delivery, birth weight, and Apgar score. Conclusions: L-Arginine load in pregnant women is associated with increased nitric oxide (NO) production and hypotension. Despite a reduced ability to produce NO, patients with preeclampsia may benefit from L-arginine supplementation. Overall, these findings partially support the hypothesis that preeclampsia is characterized by a dysfunction of the L-arginine-NO pathway. Copyright (C) 1999 Society for Gynecologic Investigation.