Osmotic Activation Of Phospholipid Biosynthetic Pathways Involves Different Regulatory Mechanisms.

CASALI, CECILIA IRENE; WEBER, KAREN; STERIN SPEZIALE, NORMA; FERNANDEZ TOME, M

carlos paz cordoba

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigación en Bioquimica y Biología Celular y Molecular; 2008

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Renal medullary collecting ducts are immersed in the highest interstitial osmolality of the body. To function they have developed various protective mechanisms. In rat renal medulla, we have shown that membrane phospholipid (PL) turnover acts as a defensive mechanism against osmolality. With the purpose of determining the molecular mechanisms that govern membrane renewal in renal cells, in the present work we studied hyperosmotic medium modulates PL synthesis and content, and the role of PLC, PKC and ERK1/2, showed to be activated by osmotic stress. MDCK cell cultures were grown during 24 h in hyperosmotic medium made by Urea, NaCl or both (NaU) addition to isotonic medium (Iso: 298, HOs: 370 to 700 mOsm/Kg H2O). PL biosynthetic activity was evaluated by measuring 14C-glycerol incorporation to PL. NaU700 caused more than 100 % increase in radiolabelled PL. The highest biosynthetic activity was associated to phosphatidylethanolamine (PE), followed by phosphatidylinositol (PI) and phosphatidylcholine (PC).Hyperosmolality increased PL content per cell and changed PL membrane profile. U73122, PLC inhibitor, decreased all 14C-PL by 30% and PKC inhibition only affected 14C-PI. ERK1/2 inhibitor U0126 selectively dropped 14C-PE by 70 %. Our data show that the PL synthesis that leads to membrane renewal and osmotic cytoprotection involves exclusive regulatory mechanisms for each PL.