Osmotic Activation Of Phospholipid Biosynthetic Pathways Involves Different Regulatory Mechanisms.

C.I. CASALI; K. WEBER; NORMA B. STERIN-SPEZIALE; M. C. FERNANDEZ-TOMÉ

Villa Carlos Paz, Córdoba

Congreso; SAIB; 2008

Renal medullary collecting ducts are immersed in the highestinterstitial osmolality of the body. To function they have developedvarious protective mechanisms. In rat renal medulla, we haveshown that membrane phospholipid (PL) turnover acts as adefensive mechanism against osmolality. With the purpose ofdetermining the molecular mechanisms that govern membranerenewal in renal cells, in the present work we studied howhyperosmotic medium modulates PL synthesis and content, and therole of PLC, PKC and ERK1/2, showed to be activated by osmoticstress. MDCK cell cultures were grown during 24 h inhyperosmotic medium made by Urea, NaCl or both (NaU) additionto isotonic medium (Iso: 298, HOs: 370 to 700 mOsm/Kg H2O). PL14 biosynthetic activity was evaluated by measuring C-glycerolincorporation to PL. NaU700 caused more than 100 % increase inradiolabelled PL. The highest biosynthetic activity was associatedto phosphatidylethanolamine (PE), followed byphosphatidylinositol (PI) and phosphatidylcholine (PC).Hyperosmolality increased PL content per cell and changed PL14 membrane profile. U73122, PLC inhibitor, decreased all C-PL by14 30% and PKC inhibition only affected C-PI. ERK1/2 inhibitor14 U0126 selectively dropped C-PE by 70 %. Our data show that thePL synthesis that leads to membrane renewal and osmoticcytoprotection involves exclusive regulatory mechanisms for each