Reductions in steroid hormone biotransformation/elimination as a biomarker of pentachlorophenol chronic toxicity

Alterations in steroid hormone metabolism by environmental endocrine disrupters can significantly affect steroid hormone-dependent processes such as growth and reproduction. The identification of biomarkers of endocrine-disrupting effects would facilitate targeting chemicals that would warrant reproductive toxicity assessment. The present study was undertaken to determine whether perturbations in steroid hormone biotransformation capabilities following short-term exposure to the endocrine-disrupting biocide pentachlorophenol (PCP) would serve as a biomarker of concentrations of this chemical that would adversely affect the reproductive capacity of Daphnia magna. Reproduction of daphnids was significantly compromised from continuous exposure to PCP concentrations as low as 0.25 mg/l. Following chronic exposure to PCP, daphnids were incubated with [C-14]testosterone and the elimination rate of several testosterone metabolites was quantified. The rate of testosterone hydroxyl-metabolite elimination was not significantly altered by PCP exposure. However, elimination of several of the glucose-conjugated metabolites of testosterone decreased in a PCP concentration-dependent manner. Adult daphnids were then exposed to these concentrations of PCP for 48 h and effects on steroid metabolism assessed. As observed following chronic exposure, PCP had no effect on the elimination of hydroxyl-metabolites of testosterone. However, PCP concentrations as low as 0.062 mg/l significantly inhibited the elimination of glucose conjugates of testosterone; and, sulfate conjugated metabolites decreased in a PCP concentration-dependent manner. These results demonstrate that: (1) PCP alters steroid hormone biotransformation/elimination capacities at concentrations that adversely affect reproduction and (2) effects on steroid hormone biotransformation can be detected following short-term exposure to PCP. Thus, this biochemical parameter may serve as a biomarker of chronic toxicity associated with PCP and perhaps other endocrine-disrupting chemicals.