Hydrogen peroxide activates ion currents in rat mesangial cells.
BACKGROUND
Hydrogen peroxide (H2O2) is an important mediator of glomerular injury, which induces proliferation and cell contraction in mesangial cells. The aim of this study was to investigate whether and which ion currents are activated during the early cellular responses to H2O2, and to study possible mechanisms of their activation.


METHODS
The effect of H2O2 on membrane voltage of mesangial cells in short-term culture was investigated with the patch clamp technique in the fast whole cell configuration.


RESULTS
H2O2 contracted mesangial cells and induced a concentration-dependent biphasic membrane voltage response. One hundred micromol/liter H2O2 led to a hyperpolarization of mesangial cells from -45 +/- 1 to -55 +/- 1 mV, which was followed by a sustained depolarization to -20 +/- 3 mV. The hyperpolarization induced by H2O2 was completely blocked by the K+ channel blocker Ba2+. In the presence of a low extracellular Cl- concentration (32 mmol/liter), the depolarization induced by H2O2 was significantly increased. The H2O2-induced depolarization was inhibited by 100 micromol/liter of the disulfide-reducing agent dithiothreitol, whereas higher concentrations of dithiothreitol (1 mmol/liter) were required to partially inhibit the hyperpolarization. Protein kinase C inhibitors blocked the H2O2-induced depolarization, but not the hyperpolarization.


CONCLUSIONS
The data indicate that H2O2 leads to a biphasic membrane voltage response in mesangial cells: an initial transient hyperpolarization, which is due to the activation of a K+ conductance, and a subsequent depolarization, which is, at least in part, due to the activation of a Cl- conductance. The oxidation of thiol groups by H2O2 is involved in the membrane voltage response, and the depolarization may be regulated by protein kinase C.
Department of Medicine, Albert-Ludwigs-University, Freiburg, Germany.
J
J
Gloy
K G
KG
Fischer
T N
TN
Meyer
P
P
Schollmeyer
R
R
Greger
H
H
Pavenstädt
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D003958:Diamide / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D004553:Electric Conductivity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007477:Ions; D016877:Oxidants / Q000494:pharmacology*; D011188:Potassium / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D019289:Pyruvic Acid / Q000494:pharmacology; D051381:Rats; D013439:Sulfhydryl Reagents / Q000494:pharmacology
D002712:Chlorides; D004791:Enzyme Inhibitors; D007477:Ions; D016877:Oxidants; D013439:Sulfhydryl Reagents; D003958:Diamide; D019289:Pyruvic Acid; D006861:Hydrogen Peroxide; D011493:Protein Kinase C; D011188:Potassium; D002118:Calcium; D004229:Dithiothreitol