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Effect of ammonium on the expression of osmosensitive genes in Madin–Darby canine kidney cells
Author(s) -
Neuhofer Wolfgang,
Vastag Monika,
Fraek MariaLuisa,
Beck FranzX.
Publication year - 2005
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2004.077784
Subject(s) - osmolyte , betaine , hsp70 , kidney , chemistry , extracellular , cotransporter , renal medulla , microbiology and biotechnology , cytoprotection , apoptosis , biology , biochemistry , heat shock protein , sodium , endocrinology , gene , organic chemistry
The cells of the kidney medulla are exposed routinely to high extracellular concentrations of various solutes including NaCl, urea and ammonium (NH 4 + ). Although it is well established that the expression of a variety of osmosensitive genes and proteins, which confer cytoprotection on renal medullary cells, is induced by high NaCl concentrations, the role of NH 4 + in these cellular responses is unclear. This study thus addressed the effect of NH 4 + on the expression of the betaine/GABA transporter (BGT‐1), the sodium/ myo ‐inositol cotransporter (SMIT), aldose reductase (AR), and heat shock protein 70 (HSP70) in Madin–Darby canine kidney (MDCK) cells, using Northern and Western blot analyses and enzyme‐linked immunosorbent assay (ELISA). The incidence of apoptosis was monitored by determining caspase‐3 activity and annexin V binding. Addition of NH 4 Cl (50 m m ; total osmolality 400 mosmol (kg H 2 O) −1 to the medium was more effective than equiosmolar NaCl in increasing BGT‐1 and HSP70 mRNA abundance, but less effective in enhancing BGT‐1 and HSP70 expression at the protein level. Qualitatively similar results were obtained for SMIT and AR mRNAs. Exposure to both isotonic and hypertonic, NH 4 Cl‐containing medium enhanced apoptosis compared with equiosmolar, NaCl‐containing media. These results suggest that, in addition to NaCl, NH 4 Cl may play a role in regulating the intracellular accumulation of organic osmolytes, the abundance of HSP70 and cell turnover in the renal medulla in vivo .