In vivo Efficacy of Ferrihydrite as an Enterosorbent for Arsenic: Short-Term Evaluation in Rodents

Abstract

The use of dietary adsorbents to reduce arsenic (As) exposure is innovative. Ferrihydrite successfully sorbs arsenite and asenate over a wide range of pH conditions and the As–ferrihydrite complexes are stable in gastrointestinal (GIT) models. Our objectives were to (1) compare structural characteristics (using x-ray diffraction and Fourier-transform infrared [FTIR] spectroscopy) and As binding affinities of industrially produced ferrihydrite (IDF) and lab-synthesized ferrihydrite and (2) evaluate the efficacy of the material displaying the best sorption capability as an As enterosorbent in a short-term mammalian model. Lab-synthesized ferrihydrite displayed superior binding affinity for both arsenate and arsenite in vitro, which led to its use in the in vivo portion of the study. Young Sprague-Dawley male rats were fed either a control diet or a 0.5% w/w ferrihydrite feed. After 1 wk of acclimation, rats were given 0.5 ml of 500 mg/L arsenate or arsenite via gavage with or without ferrihydrite. Rats were then transferred to metabolism cages, and urine collected after 24 and 48 h was analyzed for total As. Rats were evaluated daily for signs of morbidity and mortality for up to 1 wk. Ferrihydrite reduced mean urinary As levels by 74.9% and 43.6% after 24 h and 49.1% and 39.5% after 48 h for arsenite- and arsenate-treated groups, respectively. Importantly, treatment groups receiving ferrihydrite displayed no signs of As-related toxicity. All As reductions were statistically significant except for arsenate treatments at 24 h. Data suggest that, as an enterosorbent, ferrihydrite reduces bioavailability after As exposures.

Acknowledgments

This research was supported by NIEHS-P42-ES04917 and partially funded by BASF.

Notes

Present address for John F. Taylor, Weisinger Water Well, Inc., 2200 East Davis Street, Conroe, TX 77301, USA. Present address for Alicia Marroquin-Cardona is Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Nuevo León, Ave. Francisco Villa s/n Ex-Hacienda el Canadá 66050, Escobedo, Nuevo León, Mexico. Present address for Natalie Johnson is Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, 615N Wolfe St. Baltimore, MD 21205, USA.