Exploring The Endocrine Activity Of Nitrate: Does Exposure Alter Hormone Levels And Reproduction In Adult Fathead Minnows (Pimephales Promelas)?

Abstract

Endocrine disrupting compounds (EDCs) interfere with hormone production and action. EDCs typically mimic native hormones and often have a similar structure to natural hormones. While previous animal studies suggest that nitrate alters the synthesis of testosterone, nitrate is different than typical EDCs as its structure is not similar to that of any naturally occurring hormones. Given this and the environmental prevalence of nitrate, the objectives of this study are to 1) determine if nitrate acts as an EDC and 2) to better understand the mechanisms and effects of nitrate exposures onhormone production and reproduction. To achieve these objectives, groups of sexually mature adult fathead minnows were exposed to nitrate for 28 days. On days 7 and 28 of the exposure period, minnows were sacrificed for the collection of blood and gonads. The blood was used to evaluate hormone levels, while the gonads were used for gene expression analysis. Additionally, during the exposure, endpoints indicative of reproductive capabilities were also evaluated. There were no significant differences between exposure groups regarding gene expression, and there were no dose-dependent differences in egg production over the course of the breeding study.