Effect of Ochratoxin A on enzyme activities and macromolecules synthesis in MDCK cells

Protein, RNA, and DNA synthesis, and enzyme (gamma GT, LDH, LAP, A1-P, NAG) activities were assayed in Madin Darby Canine Kidney cells (MDCK) treated by ochratoxin A, a mycotoxin known to be nephrotoxic in animal and man. Both cellular macromolecules syntheses and enzymatic activities are inhibited by OTA in a dose-dependent manner after 24 h incubation. The protection by 100 microM additional phenylalanine is optimal when MDCK cells were pretreated 4 h before the poisoning by OTA. When OTA 25 microM and phenylalanine 100 microM were added simultaneously the prevention of toxic effects is evident, but not complete in spite of the respective intracellular concentrations of OTA 2.22 microM and phenylalanine 2.4 microM which are normally not in favor of a strong inhibition by OTA, except if one admits that MDCK cells are really very sensitive to OTA.