title: Troglitazone induces a cellular acidosis by inhibiting acid extrusion in cultured rat mesangial cells.
abstract: We studied the effect of troglitazone on cellular acid-base balance and alanine formation in isolated rat mesangial cells. Mesangial cells were grown to confluency in RPMI 1640 media on 30-mm chambers used to monitor both cellular pH using the pH-sensitive dye 2'7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein and metabolic acid production as well as glutamine metabolism. Troglitazone (10 microM) induced a spontaneous cellular acidosis (6.95 +/- 0.02 vs. 7.47 +/- 0.04, respectively; P < 0.0001) but without an increase in lactic acid production. Alanine production was reduced 64% (P < 0.01) consistent with inhibition of the glutamate transamination. These findings pointed to a decrease in acid extrusion rather than an increase in acid production as the underlying mechanism leading to the cellular acidosis. To test their acid extrusion capabilities, mesangial cells were acid loaded with NH and then allowed to recover in Krebs-Henseleit media or in Krebs-Henseleit media minus bicarbonate (HEPES substituted), and the recovery response (Delta pH(i)/min) was monitored. In the presence of 10 microM troglitazone, the recovery response to the NH acid load was virtually eliminated in the bicarbonate-buffered media (0.00 +/- 0.001 vs. 0.06 +/- 0.02 pH(i)/min, P < 0.0001 vs. control) and reduced 75% in HEPES-buffered media (0.01 +/- 0.01 vs. 0.04 +/- 0.02 pH(i)/min, P < 0.002 vs. control). These results show that troglitazone induces a spontaneous cellular acidosis resulting from a reduction in cellular acid extrusion.
authors: Department of Molecular and Cellular Physiology, Louisiana State University Health Science Center, Shreveport, Louisiana 71130, USA. twelbo@lsuhsc.edu
authors: Tomas
authors: T
authors: Welbourne
authors: Gan
authors: G
authors: Su
authors: Greg
authors: G
authors: Coates
authors: Robert
authors: R
authors: Routh
authors: Kevin
authors: K
authors: McCarthy
authors: Harold
authors: H
authors: Battarbee
mesh_terms: D000136:Acid-Base Equilibrium / Q000187:drug effects / Q000502:physiology*; D000143:Acids / Q000378:metabolism*; D000409:Alanine / Q000096:biosynthesis; D000818:Animals; D002478:Cells, Cultured; D002839:Chromans / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007424:Intracellular Fluid / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013844:Thiazoles / Q000494:pharmacology*; D045162:Thiazolidinediones; D000077288:Troglitazone
chemical_list: D000143:Acids; D002839:Chromans; D007004:Hypoglycemic Agents; D013844:Thiazoles; D045162:Thiazolidinediones; D019344:Lactic Acid; D000077288:Troglitazone; D000409:Alanine