ERK activation by urea in the renal inner medullary mIMCD3 cell line.
Urea- and NaCl-inducible extracellular signal-regulated kinase (ERK) phosphorylation exhibited dissimilar kinetics. Among cell lines examined, the effect of urea was unique to mIMCD3 inner medullary collecting duct cells and MDCK cells. Urea-inducible ERK activation was approximately 10-fold less sensitive to the MEK inhibitor, PD-98059, than was that of NaCl. This difference did not appear to be accounted for by differential activation of MEK isoforms. Interestingly, the inhibitor of p38 activation, SB-203580, abrogated the effect of both urea and NaCl upon both ERK and MEK activation; however, the former was much less sensitive to the inhibitor. Consistent with this observation, NaCl was much more effective than urea at inducing p38 phosphorylation. The effect of hypertonic stress (e.g., sorbitol 100 mM) could be blocked by appropriate medium dilution such that isotonicity was maintained. In marked contrast, the effect of hyperosmotic urea could not be blocked in this fashion, implying the absence of dependence upon cell volume. Together, these data suggest that cells of the renal inner medulla are potentially uniquely responsive to urea and that urea and hypertonic stressors induce ERK activation through distinct mechanisms.
Yang
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Divisions of Nephrology and Molecular Medicine, Oregon Health Sciences University and the Portland Veterans Affairs Medical Center, Portland, Oregon 97201, USA.
Zhang
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Cohen
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D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000187:drug effects* / Q000378:metabolism*; D002460:Cell Line; D004234:Diuretics, Osmotic / Q000494:pharmacology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D007679:Kidney Medulla / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D014508:Urea / Q000494:pharmacology*
D004234:Diuretics, Osmotic; D004791:Enzyme Inhibitors; D005419:Flavonoids; D047428:Protein Kinase Inhibitors; D012965:Sodium Chloride; D014508:Urea; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one