The mycotoxin ochratoxin A deranges pH homeostasis in Madin-Darby canine kidney cells.
Ochratoxin A (OTA) is a nephrotoxin which blocks plasma membrane anion conductance in Madin-Darby canine kidney (MDCK) cells. Added to the culture medium, OTA transforms MDCK cells in a manner similar to exposure to alkaline stress. By means of video-imaging and microelectrode techniques, we investigated whether OTA (1 mumol/liter) affects intracellular pH (pHi), Cl- (Cl-i) or cell volume of MDCK cells acutely exposed to normal (pHnorm = 7.4) and alkaline (pHalk = 7.7) conditions. At pHnorm, OTA increased Cl-i by 2.6 +/- 0.4 mmol/liter (n = 14, P < 0.05) but had no effect on pHi. At pHalk, application of OTA increased Cl-i by 8.6 +/- 2.6 mmol/liter (n = 10, P < 0.05) and raised pHi by 0.11 +/- 0.03 (n = 8, P < 0.05). The Cl-/HCO3- exchange inhibitor DNDS (4,4'-dinitro-stilbene-2,2'-disulfonate; 10 mumol/liter) eliminated the OTA-induced changes of pHi and Cl-i. OTA did not affect cell volume under both pHnorm and pHalk conditions. We conclude that the OTA-induced blockade of plasma membrane anion conductance increases Cl-i without changing cell volume. The driving force of plasma membrane Cl-/HCO3- exchange dissipates, leading to a rise of pHi when cells are exposed to an acute alkaline load. Thus, OTA interferes with pHi and Cl-i homeostasis leading to morphological and functional alterations in MDCK cells.
Gekle
M
M
Department of Physiology, University of Würzburg, Germany.
Vogt
R
R
Oberleithner
H
H
Silbernagl
S
S
D000818:Animals; D017920:Antiporters / Q000187:drug effects*; D001639:Bicarbonates / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D048429:Cell Size / Q000187:drug effects; D018118:Chloride Channels / Q000187:drug effects; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides / Q000378:metabolism*; D004285:Dogs; D004848:Epithelium / Q000187:drug effects; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects*; D007668:Kidney / Q000166:cytology / Q000187:drug effects*; D009793:Ochratoxins / Q000494:pharmacology*
D017920:Antiporters; D001639:Bicarbonates; D018118:Chloride Channels; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D007473:Ion Channels; D009793:Ochratoxins; C025589:ochratoxin A; D002118:Calcium