Honors Program Theses


Open Access Honors Program Thesis

First Advisor

Kavita R. Dhanwada


Atrazine is one of the most commonly used herbicides in the United States, in particular for maize crops. This herbicide is very effective against weeds. However, it has also been associated with many harmful health effects in non-target organisms such as amphibians and mammals. One of the non-target effects of atrazine may be to act as an endocrine disruptor in different cells. To study the endocrine system effects of atrazine in human cells, a human liver cell line (HepG2) was used. In this study, we determined the effects on growth of HepG2 cells after exposure to increasing concentrations of this herbicide. The MTT assay, a cell proliferation assay, was performed to assess the effects of atrazine on the growth of these cells. Atrazine concentrations as low as 156 parts per billion (ppb) with a 72 hour exposure were found to decrease the growth of the immortal HepG2 cells to statistically significant levels.

Work was also done to assess the effects on growth ofHepG2 cells after long-term exposure to atrazine. The HepG2 cells were continually maintained in atrazine-containing media. After approximately ten cell passages, MTT analysis was performed to assess the growth characteristics of these cells. While the initial results of this study are inconclusive and more experiments need to be carried out, statistically significant decreased proliferation was observed following long term exposure to low doses (3 and 100 ppb) of atrazine.

Additionally, we wanted to measure aromatase activity in atrazine treated cells to determine its endocrine effects on liver cells. It has been proposed that inducing aromatase activity is the mechanism by which atrazine disrupts the endocrine system. Microsomes from cells have been isolated and the aromatase protein has been detected in the HepG2 cells by Western blot analysis. To measure aromatase activity, a fluorescent substrate for aromatase will be incubated with microsomal protein extracts and the amount of aromatase activity will be quantitated by measuring the amount of fluorescence produced on a fluorescence spectrophotometer when the equipment is available.

Overall, it was shown that atrazine does inhibit the proliferation of the HepG2 immortal cell line. Aromatase activity leading to endocrine disruption may be involved in this inhibition of growth.

Year of Submission



Department of Biology

University Honors Designation

A thesis submitted in partial fulfillment of the requirements for the designation University Honors


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Date Original