Toxic effects of diazinon and its photodegradation products

The toxic effects of diazinon and its irradiated solutions were investigated using cultivated human blood cells (lymphocytes and erythrocytes) and skin fibroblasts. Ultra Performance Liquid Chromatography (UPLC)-UV/VIS system was used to monitor the disappearance of starting diazinon during 115-min photodegradation and formation of its by-products (diazoxon and 2-isopropyl-6-methyl-4-pyrimidinol (IMP)) as a function of time. Dose-dependent AChE and Na+/K+-ATPase inhibition by diazinon was obtained for all investigated cells. Calculated IC50 (72 h) values, in M, were: 7.5 × 10−6/3.4 × 10−5, 8.7 × 10−5/6.6 × 10−5, and 3.0 × 10−5/4.6 × 10−5 for fibroblast, erythrocyte and lymphocyte AChE/Na+/K+-ATPase, respectively. Results obtained for reference commercially purified target enzymes indicate similar sensitivity of AChE towards diazinon (IC50 (20 min)-7.8 × 10−5M), while diazinon concentrations below 10 mM did not noticeably affect Na+/K+-ATPase activity. Besides, diazinon and IMP induced increasing incidence of micronuclei (via clastogenic mode of action) in a dose-dependent manner up to 2 × 10−6 M and significant inhibition of cell proliferation and increased level of malondialdehyde at all investigated concentrations. Although after 15-min diazinon irradiation formed products do not affect purified commercial enzymes activities, inhibitory effect of irradiated solutions on cell enzymes increased as a function of time exposure to UV light and resulted in significant reduction of AChE (up to 28-45%) and Na+/K+-ATPase (up to 35-40%) at the end of irradiation period. Moreover, photodegradation treatment strengthened prooxidative properties of diazinon as well as its potency to induce cytogenetic damage.