Hopkins Marine Station Student Paper

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Title: Atrazine’s role as a multixenobiotic resistance (MXR) modulator in Mytilus californianus
Student Author(s): Stevenson, Charlotte
Faculty Advisor(s): Epel, David
Pages: 32
Location: Final papers Biology 175H
Date: June 2002
Abstract: Atrazine, a s-triazine herbicide, is the most widely used herbicide in the U.S. and is also used in over 80 countries. It is of concern since after spring rains and by leeching processes, atrazine and its breakdown products (considered equally as toxic) enter water supplies, streams, and other major bodies of water. It reaches levels in community water systems up to 89 ppb, in river basins up to 131 ppb, in drinking water up to 12 ppb, and even in rainfall up to 40 ppb. Atrazine alters neuroendocrine function, causes mammary tumors in rats, and a recent study showed demasculation and hermaphroditism in frogs at concentrations as low as 1 ppb.
This study determined whether atrazine could compromise the multixenobiotic resistance (MXR) mechanism which is a mechanism for preventing toxicants from entering cells. I found that atrazine affects the normal functioning of MXR in the gill tissue of the mussel Mytilus californianus down to a concentration of 0.6 µM (127 ppb). Atrazine's effect on development was also examined and was found to have no effect on the development of the sea urchin, Lytechinus pictus at a concentration of 2 µM (423 ppm).
The high levels of atrazine in aquatic environments due to agricultural runoff, coupled with the significant effects of atrazine on the MXR mechanism raises concern over the health of other marine organisms. Atrazine's inhibition of the MXR substrate potentially could allow other toxic or carcinogenic agents to enter cells and adversely affect the health of marine communities.