Alteration in Aquaporin 9 (AQP9) Functionality is Due to Changes in the Membrane Phospholipid Composition?

LEVI LORENA; CASTRO-PARODI MAURICIO; STERIN-SPEZIALE NORMA; DAMIANO ALICIA E

Kingston, Ontario- Canadá

Congreso; 13th International Federation of Placenta Associations; 2007

International Federation of Placenta Associations

Since the placenta is the first fetal arising organ that regulates fetal fatty acid homeostasis, the fatty acid/lipids composition in the placenta may serve as an indicator of fetal composition. We observed an increase of AQP9 expression with a lack of functionality in preeclampsia. The AQP-9 is a membrane-associated protein. It is well known that membrane protein activity can be modulated by the lipidic environment. Thus, alterations in lipid composition could induce changes in protein activity. The aim of this study was to evaluate the phospholipidic composition of preeclamptic and normal placenta membranes. Membrane vesicles were prepared by differential centrifugation. We used stopflow/light-scattering techniques to evaluate the rate of change in vesicle volume in response to an osmotic challenge and we measured the osmotic water permeability (WP). Lipids were extracted by Bligh-Dyer method, phospholipids separated by thin layer chromatography (TLC) and quantified by Fiske-Subarrow. Cholesterol was determined by enzymatic method. Results: We found a modification in WP in preeclamptic vesicles. However, this result was not correlated with an aquaporin activity. In preeclamptic placentas, the sphingomyelor concentration was higher than normal in microvilli vesicles, since the phospholipid composition was not different in basal vesicles. There were no changes in the amount of cholesterol in both vesicles between preeclapmtic and normal placentas. Conclusion: These results show that changes in the phospholipid composition may be responsible for the lack of functionality of AQP9. Further studies are needed to define the role of AQP9 in preeclampsia.