Sex differences in the bioavailability of soil-adsorbed m-xylene in orally exposed rats

Abstract

The bioavailability of soil-adsorbed m-xylene was assessed in male and female rats gavaged with an aqueous suspension of 14 C-m- xylene alone or adsorbed to sandy or clay soil. Sex-related differences were observed in the rate and the amount of m-xylene-derived radioactivity absorbed and excreted in the presence of the soils. A higher peak plasma concentration of radioactivity was observed in females following treatment with sandy soil-adsorbed m-xylene. Further, sandy and clay soil-adsorbed chemicals demonstrated significantly longer absorption half-lives ( t 1 2 ), while sandy soil produced a shorter elimination t 1 2 vs. m-xylene alone in female rats. Increased bioavailability of sandy soil-adsorbed m-xylene in females was evidenced by a significantly increased area under the plasma concentration time curve (AUC). Neither of the soils altered the maximum plasma concentration, the rate at which xylene-derived radioactivity was absorbed or eliminated, or the AUC in male rats. Fat contained the highest tissue concentration of xylenederived radioactivity in all treatment groups of both sexes. Further, in all male and female treatment groups m-xylene was primarily metabolized and excreted in urine with methyl hippuric acid identified as the main urinary metabolite. Sandy soil slightly delayed urinary excretion in females while both soils increased expired air excretion in males compared to m-xylene alone. Methylhippuric acid was the main urinary metabolite in all groups.