Study On The Toxic Mechanism For Thyroid Cells By Ammonium Perchlorate

Objective: Ammonium perchlorate (AP) is widely used in military industry and civilianchemical industry, easy to enter the body of workers through respiratory tract to affectworkers’ health. There have been some studies which have found that AP could inhibitthyroid cells from absorbing iodine as the raw material of synthesizing thyroid hormone,thus inhibit normal thyroid function, resulting in hazards on human health. This study aimsto study the toxic effect mechanisms on thyroid cells by AP and to provide a theoretical basisfor the prevention and control of AP occupational hazard via exposing normal human thyroidcells Nthy-ori3-1cultured in vitro to AP.Methods: The normal human thyroid cells Nthy-ori3-1were cultured in incubator with5%CO2at37℃to logarithmic growth phase, then the cells were inoculated to culture platesand continued to be fostered. The cells in culture plates were exposed to AP at the doses of0,5,10,20,40,60mmol/L respectively when they grown to logarithmic phase, then themorphological changes were observed and the cells and supernatant were collected todetermine the following indicators. Cell survival rates were assessed by thiazolyl bluecolorimetric method (MTT assay); lactate dehydrogenase (LDH), superoxide dismutase(SOD), malondialdehyde (MDA) levels were determined by colorimetry; cell apoptosis rateswere determined by flow cytometry technology; the concentrations of thyroglobulin (Tg)were measured using enzyme-linked immunosorbent assay (ELISA).Results: With increase in AP exposure dose, adherent ability of cells in each AP exposuredose group were all weaker than that in control group, floating cells increased, cell densitydecreased, cell volume reduced, and cell shape turned to round or irregular from long shuttlegradually; however, the abnormal changes above were not observed in control group. When cells were exposed to AP at a dose of60mmol/L for12h,24h,48h and72h, cell survivalrates were respectively74.93%,42.26%,2.66%and0.99%, when cells were exposed to APat a dose of60mmol/L for24h,48h and72h, cell survival rates were respectively73.15%,30.91%and3.03%, all significantly lower than that in control group (100%)(P<0.05orP<0.01). LDH activity in cell culture solution increased with AP doses increased, LDHactivity of40mmol/L dose group was0.70U/mL, significantly higher than that in controlgroup (0.55U/mL)(P<0.01). The cell apoptosis rates increased with AP doses increased, thetotal cell apoptosis rates of10,20,40and60mmol/L dose group were respectively23.04%,24.27%,24.40%and33.50%, significantly higher than that in control group (15.66%)(P<0.01); the early cell apoptosis rates of20,40and60mmol/L dose group wererespectively15.70%,15.84%and16.96%, significantly higher than that in control group(9.54%)(P<0.05or P<0.01); the late cell apoptosis rate of60mmol/L dose group was16.54%, significantly higher than that in control group (6.11%)(P<0.01). With increase inAP exposure doses, MDA contents in cell culture solution of each dose group tended todecrease, while compared to control group (2.36nmol/mL), only5mmol/L dose group(1.08nmol/mL) showed a statistics difference (P<0.05); SOD activity in cell culture solutionof each dose group showed no statistics difference compared to control group (P>0.05); Tgconcentration in cell culture solution of each dose group tended to decrease, but compared tocontrol group, showed no statistics difference (P>0.05).Conclusion: Via cultured human normal thyroid cell Nthy-ori3-1in vitro, the study showedthat AP could cause cell morphology changes, inhibit cell survival rate, elevate LDH activityin cell culture solution, and induce human thyroid cells apoptosis, demonstrated that AP hadtoxic effect on human thyroid cells and could cause damage to human thyroid cells.