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The mycotoxin ochratoxin A deranges pH homeostasis in Madin-Darby canine kidney cells
M Gekle1, R Vogt, H Oberleithner
1Department of Physiology, University of Würzburg, Germany.
Abstract:
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.
Insights
Ochratoxin A (OTA) blocks anion channels in kidney cells, increasing intracellular chloride and altering pH. This toxin disrupts cell homeostasis, impacting kidney cell function and morphology.
Area of Science:
- Nephrology
- Cell Physiology
- Toxicology
Background:
- Ochratoxin A (OTA) is a nephrotoxin known to affect kidney cells.
- OTA exposure mimics alkaline stress in Madin-Darby canine kidney (MDCK) cells.
- The precise effects of OTA on intracellular pH (pHi), chloride (Cl-i), and cell volume remain to be fully elucidated.
Purpose of the Study:
- To investigate the impact of Ochratoxin A on intracellular pH, chloride levels, and cell volume in MDCK cells.
- To determine if OTA affects MDCK cells under normal and alkaline conditions.
- To understand the role of anion conductance in OTA-induced cellular changes.
Main Methods:
- Utilized video-imaging and microelectrode techniques to monitor MDCK cells.
- Applied Ochratoxin A (1 µmol/L) to cells under normal (pH 7.4) and alkaline (pH 7.7) conditions.
- Assessed changes in intracellular pH (pHi), intracellular chloride (Cl-i), and cell volume.
Main Results:
- OTA increased Cl-i by 2.6 mmol/L at normal pH and by 8.6 mmol/L at alkaline pH.
- OTA elevated pHi by 0.11 units under alkaline conditions.
- The Cl-/HCO3- exchange inhibitor DNDS abolished OTA-induced changes, and OTA did not alter cell volume.
Conclusions:
- Ochratoxin A blocks plasma membrane anion conductance, increasing intracellular chloride without affecting cell volume.
- OTA disrupts the driving force of Cl-/HCO3- exchange, leading to increased pHi during alkaline stress.
- OTA interferes with pHi and Cl-i homeostasis, causing morphological and functional alterations in kidney cells.