Induction of genotoxic effects and modulation of the intracellular calciumlevel in syrian hamster embryo (SHE) fibroblasts caused by ochratoxin A

The mycotoxin ochratoxin A (OTA) is a naturally occuring contaminant of foo d. The genotoxic status of OTA is still controversial because contradictory results were obtained in various microbial and mammalian gene mutation ass ays. In this study, OTA was investigated to examine its potency to induce m icronuclei (MN) in SHE cells. The SHE-micronucleus assay revealed that OTA induces MN in a dose- and time-dependent manner. The results of kinetochore analysis revealed that mainly clastogenic events are involved in OTA genot oxicity. Induction of mitotic disturbances can be closely related to change s of the intracellular calcium concentration ([Ca2+](i)). The investigated time course of OTA-induced [Ca2+](i) changes revealed that the obtained sig nal is a short spike signal resembling physiological responses. In the abse nce of extracellular calcium, a long-lasting signal indicates possible dama ge to intracellular calcium stores or channels. Our data show that the OTA- induced [Ca2+](i) rise is caused by Ca2+-release from intracellular stores as well as Ca2+ influx from extracellular area. Finally, the influence of t he changed intracellular calcium level on the actin cytoskeleton was invest igated. Visualization of the actin filaments revealed time- and concentrati on-dependent effects. Cell shrinkage and depolymerized filaments were obser ved. We conclude that OTA disrupts actin filaments by a direct irreversible binding to actin. (C) 1999 Elsevier Science Ltd. All rights reserved.