Bushra Khan

Stereoselective sorption by agricultural soils and liquid-liquid partitioning of trenbolone (17α and 17β) and trendione.

Trenbolone acetate (TBA) is a synthetic anabolic hormone used for growth promotion in beef cattle, which excrete primarily 17alpha-trenbolone along with small amounts of 17beta-trenbolone and trendione. To aid in predicting transport of manure-borne TBA metabolites, multiconcentration sorption isotherms for 17alpha- and 17beta-trenbolone and trendione were generated with five autoclaved-sterilized soils that represented a range in soil properties. Hormone concentrations were measured independently in solution and soil phases, and quantified using liquid chromatography with electrospray mass spectrometry. In addition, partition coefficients between apolar hexane and water (K(hw)) and bipolar octanol and water (K(ow)) were measured for the three androgens to better ascertain the mechanisms that may be responsible for the sorption differences observed between isomers. In all five soils, trendione sorbed the most, and 17alpha- and 17beta-trenbolone isomers exhibited different sorption magnitudes. 17beta- trenbolone consistently sorbed a factor of 2 more than 17alpha-trenbolone. For all three androgens, sorption is proportional to the soil organic carbon (OC) content with average log OC-normalized distribution coefficients (log K(oc), L/kg OC) of 2.77 +/- 0.12 for 17alpha-trenbolone, 3.08 +/- 0.1 for 17beta-trenbolone and 3.38 +/- 0.19 for trendione, which suggests the dominance of hydrophobic partitioning. However, differences in K(hw) values between 17alpha- and 17beta-trenbolone were small indicating differences are not simply due to differences in aqueous activity. In contrast, similarly different K(ow) and K(oc) values for the two isomers indicate the likely contribution of H-bonding to stereoselective sorption.

Soil temperature and moisture effects on the persistence of synthetic androgen 17α-trenbolone, 17β-trenbolone and trendione

Trenbolone acetate (TBA) is a synthetic androgenic steroid hormone administered as a subcutaneous implant for growth promotion in beef cattle. The primary metabolite excreted in manure from implanted cattle is 17alpha-trenbolone with lesser amounts of 17beta-trenbolone and trendione also present. At 22 degrees C and favorable moisture conditions in a controlled laboratory environment, trenbolone degrades to trendione in a few hours; however, these conditions are often not what exist in the field. Therefore, aerobic degradation rates of 17alpha-trenbolone, 17beta-trenbolone and trendione were determined in a sandy soil and silty clay loam under a range of temperature and water availability combinations that may be expected in the field. A first-order exponential decay model was used to estimate rates and generally resulted in good model fits to the data. Degradation rates decreased with decreasing water availability (i.e., more negative soil matric potential) and decreasing temperature. However, when water availability was substantially reduced (-1.0MPa), hotter temperatures (35 degrees C) significantly reduced trenbolone degradation rates. Once temperature was low enough to limit microbial activity, no further changes were observed with decreasing matric potential. Trendione also exhibited similar moisture and temperature dependent degradation, but persisted longer than the parent trenbolone. The latter was discussed in light of extracellular versus intracellular enzymatic degradation and sorption. Half lives at colder temperatures (5 degrees C) even under favorable moisture conditions were 2-3d for the trenbolone isomers and approached 10d for trendione.

Evaluating stereoselective sorption by soils of 17α-estradiol and 17β-estradiol.

The application of manure and biosolids onto agricultural land has increased the risk of estrogenic exposure to aquatic systems. Both αE2 and βE2 have been routinely detected in surface and ground waters with higher concentrations reported near concentrated animal feeding operations and agricultural fields. Although movement through the soil to a water body is highly dependent on hormone-soil interactions, to date, only the interaction of βE2 with soils has been characterized despite αE2 often being the more common form excreted by livestock such as beef cattle and dairy. In predicting the transport of estradiol, sorption characteristics for the stereoisomers have been assumed to be the same. To evaluate this assumption, sorption of αE2 and βE2 was measured on seven surface soils representing a range in soil properties. Soils were autoclave-sterilized to minimize loss due to biotransformation, and both solution and soil phase concentrations were measured. Overall, E2 sorption is best correlated to soil organic carbon (OC) with an average log OC-normalized distribution coefficient (logKoc, L kgoc(-1)) of 2.97±0.13 for αE2 and 3.14±0.16 for βE2 with βE2 consistently exhibiting higher sorption than αE2 with the highest β/α sorption ratio of 1.9. Assuming that the two isomers sorb the same is not a conservative decision making approach. The lower sorption affinity of αE2 increases the likelihood that it will be leached from agricultural fields.

Estrogens and synthetic androgens in manure slurry from trenbolone acetate/estradiol implanted cattle and in waste-receiving lagoons used for irrigation.

The increasing size of concentrated animal feeding operations has led to a concomitant increase in the land-application of manure, which has spawned research on the concentrations and environmental risk assessment of natural and synthetic hormones in animal manures. 17β-Trenbolone acetate (TBA) is widely used in the United States for improving daily gains in beef cattle and is often administered in combination with 17β-estradiol (17β-E2). Trenbolone (TB) and E2 isomers and their metabolites were quantified in manure collection pits and lagoon effluent from beef cattle implanted with the commercial anabolic preparation Ravoler-S (containing 140 mg 17β-trenbolone acetate and 28 mg 17β-E2). Manure pit and lagoon effluent samples were collected weekly for 9 weeks post implanting and analyzed using reverse-phase liquid chromatography tandem mass spectrometry. 17α-TB was the most abundant androgen with the highest concentration observed 2 weeks post implant. 17β-TB and trendione peaked at the end of week 2 and 4, respectively. For the estrogens, the highest concentrations for estrone (E1), estriol (E3), and 17α-E2 were observed after week 4, 6, and 8, respectively. 17β-E2 concentrations were the lowest of the estrogens and erratic over time. In lagoon water, which is used for irrigation, 17α-TB and E1 had the highest detected hormone concentrations (1.53 and 1.72 μg L(-1), respectively). Assuming a 1-2 order dilution during transport to surface water, these hormone levels could lead to concentrations in receiving waters that exceed some of the lowest observable effect levels (LOELs) reported for hormones (e.g., 0.01-0.03 μg L(-1)).

Prediction and experimental evaluation of soil sorption by natural hormones and hormone mimics.

Surface runoff from manure-fertilized fields is a significant source of endocrine-disrupting compounds (EDCs) in the environment. Sorption by soils may play a major role in the environmental fate of manure-borne EDCs, including 17α- and 17β-estradiol (17α-E2 and 17β-E2), estrone (E1), melengestrol acetate (MGA), 17α- and 17β-trenbolone (17α-TB and 17β-TB), trendione (TND), and zeranol (α-ZAL). As a measure of sorption behavior, the organic carbon-normalized partition coefficients (K(OC)) of 17β-E2, E1, MGA, and α-ZAL were experimentally determined for three agricultural soils with initial EDC concentrations spanning from ∼0.01 to >1 μM. Sorption isotherms were linear for most solute-soil combinations. Measured K(OC) values were compared to those predicted using a suite of single-parameter and polyparameter linear free energy relationships (sp- and pp-LFERs). Sp-LFER models were based on experimentally determined octanol-water partition coefficients (K(OW)), whereas pp-LFER solute descriptors were calculated indirectly from experimentally determined solvent-water partition coefficients or the program ABSOLV. Log K(OC) predictions by sp-LFERs were closest to the experimentally determined values, whereas pp-LFER predictions varied considerably due to uncertainties in both solute and sorbent descriptors determined by ABSOLV or estimates using the partition coefficient approach.

Suppression of humoral immune responses by 2,3,7,8-tetrachlorodibenzo-p-dioxin intercalated in smectite clay

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a highly toxic environmental contaminant found in soils and sediments. Because of its exceptionally low water solubility, this compound exists predominantly in the sorbed state in natural environments. Clay minerals, especially expandable smectite clays, are one of the major component geosorbents in soils and sediments that can function as an effective adsorbent for environmental dioxins, including TCDD. In this study, TCDD was intercalated in the smectite clay saponite by an incipient wetness method. The primary goal of this study was to intercalate TCDD in natural K-saponite clay and evaluate its immunotoxic effects in vivo. The relative bioavailability of TCDD was evaluated by comparing the metabolic activity of TCDD administered in the adsorbed state as an intercalate in saponite and freely dissolved in corn oil. This comparison revealed nearly identical TCDD-induced suppression of humoral immunity, a well-established and sensitive sequela, in a mammalian (mouse) model. This result suggests that TCDD adsorbed by clays is likely to be available for biouptake and biodistribution in mammals, consistent with previous observations of TCDD in livestock exposed to dioxin-contaminated ball clays that were used as feed additives. Adsorption of TCDD by clay minerals does not appear to mitigate risk associated with TCDD exposure substantially.