AbstractLocal accumulation of xenobiotics in human and animal tissues may cause adverse effects. Large differences in their concentrations may exist between individual cell types, often due to the expression of specific uptake and export carriers. Here we established a two-photon microscopy-based technique for spatio-temporal detection of the distribution of mycotoxins in intact kidneys and livers of anesthetized mice with subcellular resolution. The mycotoxins ochratoxin A (OTA, 10 mg/kg b.w.) and aflatoxin B₁ (AFB₁, 1.5 mg/kg b.w.), which both show blue auto-fluorescence, were analyzed after intravenous bolus injections. Within seconds after administration, OTA was filtered by glomeruli, and enriched in distal tubular epithelial cells (dTEC). A striking feature of AFB₁ toxicokinetics was its very rapid uptake from sinusoidal blood into hepatocytes (t_1/2 ~ 4 min) and excretion into bile canaliculi. Interestingly, AFB₁ was enriched in the nuclei of hepatocytes with zonal differences in clearance. In the cytoplasm of pericentral hepatocytes, the half-life (t_1/2~ 63 min) was much longer compared to periportal hepatocytes of the same lobules (t_1/2 ~ 9 min). In addition, nuclear AFB₁ from periportal hepatocytes cleared faster compared to the pericentral region. These local differences in AFB₁ clearance may be due to the pericentral expression of cytochrome P450 enzymes that activate AFB₁ to protein- and DNA-binding metabolites. In conclusion, the present study shows that large spatio-temporal concentration differences exist within the same tissues and its analysis may provide valuable additional information to conventional toxicokinetic studies.