The role of sphingolipids in MDCK cells polarization submitted to hypertonic stress

PESCIO L; LEOCATA NIETO F; FERNÁNDEZ TOME M; STERIN SPEZIALE N

Rosario , Santa Fe, Argentina

Congreso; XLII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research; 2006

SAIB

Renal papilla plays a key role in water and electrolytic homeostasis since regulates urinary pH and ionic concentration. These functions are carried out by papillary collecting ducts constituted by highly polarized epithelial cells which present two membrane domains, apical and basolateral. Both domains show different lipid composition: high concentration of glycosphingolipids (GSL) in apical domain while basolateral is enriched in sphingomyelin (SM). It has been reported that during renal development hypertonicity induces differentiation of tubular structures which implies cellular polarization, but the mechanism involved is not well understood. In order to explore the role of sphingolipids (SL) in renal epithelial differentiation, we studied SL metabolism and gp135 expression, as polarization parameter, in MDCK cells submitted to hypertonicity. Cultures were grown in high NaCl media (250 mM) for 24 and 48 hs in presence of 14CPalmitic acid or 14C-Galactose to monitor de novo SL and GSL synthesis, respectively. Total 14C-Palmitic acid incorporation to SLs was significantly higher in cells under hypertonicity, even more at 48 hs. SM labeling registered the mayor increase. Similarly, GSL synthesis was also increased in hypertonic conditions. Increased SLs metabolism preceded gp135 protein in apical membranes suggesting early sphingolipid participation in cell polarization.