CONICET | Buscador de Institutos y Recursos Humanos

Abstract Hyperosmolality is a key signal for renal physiol- ogy. On the one hand, it contributes to the differentiation of renal medullary structures and to the development of the urinary concentrating mechanism. On the other, it is a stress factor. In both cases, hyperosmolality activates processes that require an adequate extension of cellular membranes. In the present work, we examined whether hyperosmolality regulates phospholipid biosynthesis, which is needed for the membrane biogenesis in the renal epithelial cell line Madin-Darby canine kidney (MDCK). Because phospholip- ids are the structural determinants of all cell membranes, we evaluated their content, synthesis, and regulation in MDCK cultures subjected to different hyperosmotic con- centrations of NaCl, urea, or both. Hyperosmolality in- creased phospholipid content in a concentration-dependent manner. Such an effect was exclusively due to changes in NaCl concentration and occurred at the initial stage of hy- perosmolar treatment concomitantly with the expression of the osmoprotective protein COX-2. The hypertonic upregu- lation of phosphatidylcholine (PC) synthesis, the main con- stituent of all cell membranes, involved the transcriptional activation of two main regulatory enzymes, choline kinase (CK) and cytidylyltransferase (CCT ) and required ERK1/2 activation. Considering that physiologically, re- nal medullary cells are constantly exposed to high and vari- able NaCl, these findings could contribute to explaining how renal cells could maintain cellular integrity even in a nonfavorable environment .Casali, C. I., K. Weber, N. O. Favale, and M. C. F. Tome. Environmental hyperosmolality regulates phospholipid biosynthesis in the renal epithelial cell line MDCK.