Ochratoxin A decreases the activity of phosphoenolpyruvate carboxykinase and its mRNA content in primary cultures of rat kidney proximal convoluted tubule cells.

The effect of ochratoxin A on the specific activities of phosphoenolpyruvate carboxykinase, gamma-glutamyl transpeptidase and phosphate-dependent glutaminase were investigated in primary cultures of rat kidney proximal convoluted tubule cells grown in a serum-free medium supplemented with growth factors. Addition of ochratoxin A (25-100 microM) to the medium caused reduction in the specific activities of phosphoenolpyruvate carboxykinase and gamma-glutamyl transpeptidase only. Addition of cAMP caused a four-fold increase in the concentration of phosphoenolpyruvate carboxykinase mRNA in tubule cells within 3 h. This cAMP-mediated increase in phosphoenolpyruvate carboxykinase mRNA content was abolished when ochratoxin A was added simultaneously.