The herbicide atrazine is the second most widely used weedkiller in the U.S., applied to corn and sorghum fields throughout the Midwest and also spread on suburban lawns and gardens. It was banned in Europe after studies linked the chemical to endocrine disruptions in fish and amphibians.
The UCSF study is the first to identify its full effect on human cells. It is being reported in the May 7 issue of the journal “PLoS ONE.”
In studies with human placental cells in culture, the UCSF scientists found that atrazine increased the activity of a gene associated with abnormal human birth weight when over-expressed in the placenta. Atrazine also targeted a second gene that has been found to be amplified in the uterus of women with unexplained infertility.
In parallel studies of zebrafish, a widely used animal in development studies, the research team showed that atrazine “feminized” the fish population – increasing the proportion of fish that developed into females. In water with atrazine concentrations comparable to those found in runoff from agricultural fields, the proportion of female fish increased two-fold. Environmental factors are known to influence the sex of zebrafish and many other fish and amphibians as they develop.
“These fish are very sensitive to endocrine disrupting chemicals, so one might think of them as ‘sentinels’ to potential developmental dangers in humans,” said Holly Ingraham, PhD, senior author on the study and a UCSF Professor of Cellular and Molecular Pharmacology. “These atrazine- sensitive genes are central to normal reproduction and are found in steroid producing tissues. You have to wonder about the long-term effects of exposing the rapidly developing fetus to atrazine or other endocrine disruptors.”
Ingraham intends to determine precisely how atrazine affects human and other mammalian endocrine cells and why these cells are particularly sensitive to it. She notes that bisphenol A, a compound in many hard plastic consumer products, is also an endocrine disrupter and is now under increased study for its safety. In April, Canada announced a decision to ban sale of consumer products with bisphenol A.
The lead author of the study is Miyuki Suzawa, a postdoctoral fellow in Ingraham’s lab.
UCSF researchers exposed sexually immature zebrafish to atrazine and other chemicals for different periods of time. They found that exposure to atrazine for 48 hours at concentrations that might be found in water containing agricultural runoff, produced twice as many female fish.
Through genetic analysis, they found that atrazine preferentially activates a class of receptors in the cell nucleus, including two known as SF-1 and LRH-1. SF-1 regulates production of enzymes involved in the synthesis of steroids in the body and development of many endocrine tissues. One of these enzymes, known as Aromatase, plays a role in determining whether lower vertebrates, such as fish will become male or female. Aromatase is known as a feminizing enzyme.
In the human placental cell culture studies, the scientists found that a 24-hour exposure to atrazine activates a cluster of genes involved in hormone signaling and steroid synthesis.
They report, “Endocrine-related cell types with a capacity for steroid generation appear to be especially sensitive (to Atrazine), as demonstrated by the “exquisite” cellular specificity of the atrazine response.”
The finding that a pervasive and persistent environmental chemical appears to significantly change hormone networks means that scientists must take a broader look at this herbicide’s potential effect on human health, Ingraham said. Up to now, much of the focus has been on breast cancer, but since proper development of the endocrine system is important for normal reproduction, stress responses and metabolism, early exposure to this chemical in a fetus or infant might alter normal physiology later in life, she said.
Wallace Ravven | EurekAlert!
The hidden structure of the periodic system
17.06.2019 | Max-Planck-Institut für Mathematik in den Naturwissenschaften (MPIMIS)
Tiny probe that senses deep in the lung set to shed light on disease
17.06.2019 | University of Edinburgh
The well-known representation of chemical elements is just one example of how objects can be arranged and classified
The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...
Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.
Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...
Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.
The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...
Discovery by Brazilian and US researchers could change the classification of two species, which appear more akin to jellyfish than was thought.
The tube anemone Isarachnanthus nocturnus is only 15 cm long but has the largest mitochondrial genome of any animal sequenced to date, with 80,923 base pairs....
Researchers at Chalmers University of Technology, Sweden, have discovered a completely new way of capturing, amplifying and linking light to matter at the nanolevel. Using a tiny box, built from stacked atomically thin material, they have succeeded in creating a type of feedback loop in which light and matter become one. The discovery, which was recently published in Nature Nanotechnology, opens up new possibilities in the world of nanophotonics.
Photonics is concerned with various means of using light. Fibre-optic communication is an example of photonics, as is the technology behind photodetectors and...
29.04.2019 | Event News
17.04.2019 | Event News
15.04.2019 | Event News
17.06.2019 | Information Technology
17.06.2019 | Earth Sciences
17.06.2019 | Ecology, The Environment and Conservation