OBJECTIVE: To investigate the ex vivo platelet aggregation in response to a substrate (L-arginine [L-Arg]) and a donor (sodium nitroprusside [SN]) of nitric oxide (NO) in nonpregnant women and in normotensive pregnancies. METHODS: Platelet aggregation was studied with a dual-channel aggregometer and expressed as a percentage of light transmission. Measurements were done at baseline and after preincubation with scalar doses of L-Arg and SN. The intraplatelet L-citrulline (L-Cit) levels were measured by high-performance liquid chromatography (HPLC). RESULTS: In both groups, the baseline aggregation values were similar for adenosine diphosphate (ADP) and collagen stimuli. Wilcoxon rank-sum testing demonstrated that in both groups the addition of L-Arg had a significant effect on aggregation: Doses of 50 to 5000 mumol decreased ADP-induced aggregation. Conversely, collagen-induced aggregation was affected only by the highest dose of L-Arg. Sodium nitroprusside administered in doses of 2.5 to 250.0 nmol decreased ADP- and collagen-induced platelet aggregation equally. ADP-induced aggregation values obtained after (SN) incubation were positively correlated with gestational age. Intraplatelet L-Cit levels showed a significant rise after the incubation with L-Arg, and this effect was negatively correlated with gestational age. CONCLUSION: The L-Arg-NO system regulates platelet aggregation during pregnancy. Moreover, a physiologic reduction of platelet sensitivity to the antithrombotic effect of NO occurs.

Adenosine Diphosphate↗

PubMedDate not supplied

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.

Adult↗

PubMedDate not supplied

[Comparative evaluation of various pharmacokinetic parameters of tetracycline, orally administered alone or in combination with triacetyloleandomycin].

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Adult↗