Atrazine body burdens and endocrine correlates in channel catfish (Ictalurus punctatus) and yellow perch (Perca flavescens) from Old Woman Creek and Lake Eric

  • Lynn, Scott (PI)

Grants and Contracts Details


Environmen~al p~llution is .au~iquitous problem that has diverse effects at many dIfferent levels of bIOlogIcal orgamzatIOn. There are several coastal estuarine sites in the US with substantial herbicide contamination (Pennington et al. 2001, Clark and Goolsby ~OOO,!lannon-Fetcho et al. 1999, Pereira et al. 1996, Kucklick and Bidleman 1994), mcludmg Old Woman Creek (OWC) National Estuarine Research Reserve in East Huron , OH. OWC has significant herbicide contamination from agricultural upland runoff, with atrazine (a chloro-S-triazine herbicide) being one of the most prevalent (K Kreiger pers comm). Richards et al. (1996) found the annual total load, for five tributaries near OWC, of atrazine, the highest ofthe five herbicides measured, ranged from 500-20,000 kg/yr. Atrazine is the most commonly used pesticide in the US and, like many pollutants, is an endocrine disrupting chemical (EDCs): a chemical that disrupts an organisms endocrine system (Crisp et al. 1998). EDCs most notoriously effect the function of steroid or sex honnones, the most common being estrogen mimics (Datson et al. 1997). Atrazine is a suspected environmental estrogen, inducing aromatase activity, the rate-limiting enzyme in the conversion of androgens to estrogens (Sanderson et al. 2000). However, Danzo (1997) found that atrazine reduced [3H]5 alpha-DHT (the most active fonn of testosterone) binding to the androgen-binding protein by 40%, indicating an antiandrogen mechanism of action. There is a glaring lack of knowledge on the exact endocrinological effects of atrazine exposure in aquatic vertebrates. Most research on estrogenic EDCs has focused on how they confound reproduction, such as Nichols et al. (2001), however, the pituitary gland is regulated by estrogen and its function can theoretically be altered by estrogenic EDCs. Atrazine was shown to affect the hypothalamic control of the pituitary-ovary endocrine axis in Long- Evans hooded rats leading to a suppression in circulating plasma prolactin levels (Cooper et al. 2000). However, O'Connor et al. (2000) found that atrazine increased prolactin levels in female rats. Osmoregulation, an important homeostatic function, is principally regulated by the pituitary honnones (prolactin (PRL) and growth honnone (GH», as well as other pituitary-dependant honnones (cortisol and the insulin-like growth factors (IGF) -I and -II) (Eckert et al. 2001). Prolactin is known to contribute to ion retention by changing the activity of enzymes in gill chloride-secreting cells (Bentley 1998). Additionally, Prasad and Reddy (1994) found that atrazine exposure produced disturbances in the hydromineral balance of Tilapia mossambieus and Hussein et al. (1996) showed decreases in serum sodium, chloride and potassium ion concentrations in Chrysiehthyes auratus and Oreoehromis nilotieus. The importance of osmoregulation becomes more dramatic in fish in saltwater-freshwater estuaries, especially if the fish's ability to adapt to the salinity fluctuations becomes severely challenged. It has also been shown that the enzymatic controls of osmoregulation in Perea flaveseens are temperature and seasonally dependent (Packer and Garvin 1998). Yellow perch are an important species both ecologically and economically, especially in the Lake Erie area (Malison 1999). They also have a unique sexual dimorphism, an estrogen dependant process, wherein females grow faster than males (Malison et al. 1988). Channel catfish are an excellent species for studying environmental contamination, as they are obligate benthic dwelling fish (Weisberg and Janicki 1990) (giving them a higher exposure to sediment associated pollutants, such as atrazine) and are a moderately tolerant species (Howe et al. 1998). Channel catfish are found in relative abundance at OWC, using the estuary as a nursery and spawning ground (Herdendorf et al. 2001). Yellow perch are not as common in OWC but do use the estuary as a nursery and feeding ground. These two species represent different trophic levels, as channel catfish are mainly carnivorous and omnivorous, while yellow perch adults are piscivorous and top predators (Paszkowski and Tonn 1994). Studies are recently showing that biomarkers or bioindicators can be used as sentinels of exposure, but are not sensitive indicators of physiological end-points such as reproduction (Cheek et al. 2001, Petrulis et al. 2001). There are also subtle endocrine effects of some EDCs that biomarkers are unable to detect (Moore and Lower 2001 and Park et al. 2001). Thus, there is a need to characterize the response of the endocrine system to toxicological insults in order to understand and predict physiological consequences ofEDCs. Wepropose that EDCs (like steroids) can affect the regulation of the pituitary hormones (directly and indirectly) that control teleost growth, reproduction, development, and osmoregulation. To support this hypothesis, we intend to collect channel catfish (Ictalurus punctatus) and yellow perch (Perca flavescens) from OWC and Lake Erie, and to analyze for atrazine body burdens, plasma hormone levels (using radioimmuno-assays (RIAs)) and tissue specific mRNA expression levels (using molecular cloning, hybridization studies and RT-PCR). Our aim is to elucidate the manner in which toxicants influence the animal's endocrine status, but more importantly, the potential latent effects that result from toxicant exposure. This work, coupled with the laboratory studies I propose to conduct as part of my PhD dissertation, will illuminate the endocrine pathways that underlie the sub-lethal as well as overt effects of atrazine on catfish and yellow perch physiology. Our goals are 1.) to compare atrazine body burdens, plasma hormone levels and tissue specific mRNA expression from both species offish at two separate sites (OWC and Lake Erie) and 2.) to determine seasonal and annual patterns ofatrazine body burdens, plasma hormone levels and tissue specific mRNA expression in both species of
Effective start/end date6/1/025/31/05


Explore the research topics touched on by this project. These labels are generated based on the underlying awards/grants. Together they form a unique fingerprint.