RESUMO
PURPOSE: To evaluate placental function and perfusion in a rat model of preeclampsia infused with L-nitro-arginine methyl ester (L-NAME) by dynamic contrast-enhanced (DCE) MRI using gadolinium chelates. METHODS: Pregnant female Sprague-Dawley rats were fitted on embryonic day 16 (E16) with subcutaneous osmotic minipumps loaded to deliver, continuously, L-NAME (50 mg/day per rat; case group) or saline solution (control group). DCE MRI was performed on E19 using gadolinium chelates and a 4.7-T MRI apparatus for small animals. Quantitative analysis was performed using an image software program: placental blood flow (perfusion in mL/min/100 mL of placenta) and fractional volume of the maternal vascular placental compartment (ratio between the placental blood volume and the placental volume, Vb in %) were calculated by compartmental analysis. RESULTS: A total of 176 placentas (27 rats) were analyzed by DCE MRI (97 cases and 79 controls). The model was effective, inducing intrauterine growth retardation, as there was a significant difference between the two groups for placental weight (p < 0.01), fetal weight (p = 0.019), and fetal length (p < 0.01). There was no significant difference in placental perfusion between the L-NAME and control groups (140.1 ± 74.1 vs. 148.9 ± 97.4, respectively; p = 0.496). There was a significant difference between the L-NAME and control groups for Vb (53 ± 12.9 vs. 46.7 ± 9%, respectively; p < 0.01). CONCLUSION: In the L-NAME preeclampsia model, placental perfusion is normal and the fractional blood volume is increased, suggesting that preeclampsia is not always expressed as a result of decreased placental perfusion. This highlights the usefulness of MRI for investigating the physiopathology of preeclampsia.
