L-arginine displays antithrombotic effects through nitric oxide release in pregnant women

OBJECTIVE: Nitric Oxide (NO) has antiaggregating properties. Our aim was to evaluate if a load of I-Arginine (ARG), the substrate for NO production, could affect platelet aggregation in pregnancv. STUDY DESIGN: After informed consent, 9 healthy women in follicular phase (('.) and 8 women with uncomplicated pregnancy (P) at 3Q-36th week were infused with i.v. ARG <30g/30 min). Blood samples were taken before and 15. 30, 60, & 90 min thereafter. Aggregation was evaluated in vitro through the addition of ADP (2jJiM) or Collagen (4fxg/ml) to platelet-rich plasma, hv using a dual channel aggregometer. I-Citrulline (CIT) levels wert- evaluated in ihe serum bv using HPI.C with fluorimetric detection. RESULTS: In group C, ARG infusion significantly and transiently inhibited platelet aggregation induced by both ADP (from 65 ±5.5% to 42 ±10.4%) and Collagen (from 70.4 ±'.5.4% to 56.4 ±7.3%) (p < 0.01 at 15tb min, for either stimulations). In group P a similar effect was observed, lasting also at 30th min of infusion. However, the reduction of aggregation induced bv ARG in C (ADP -28% & Collagen -19%, in respect with baseline) was wider than in P group (ADP -13% & Collagen - 11%, I' < 0.05). In both C (from 32.3 ±4.2 jtM/L to 71.6 ±9.2) and P groups (from 31.1 ±3.6 to 53.1 ±6.8) CIT levels were increased at 30th min (P < 0.02). The increase in P group (65%) was of lower magnitude than in C (112%, p < 0.05). CONCLUSIONS: ARC. load in pregnant women as well as in non-pregnani controls is able to reduce the platelet aggregation, tested in vitro. Such an amithrombotic effect is correlated with an up-regulation of NO svnthase whose magnitude is reduced in pregnancy.