Embryonic Effects of Androgen Active Endocrine Disrupting Chemicals on Avian Immune and Reproductive Systems

Abstract

Endocrine disrupting chemicals (EDCs) are compounds that alter the production, secretion, action, and elimination of endogenous hormones. In the environment, organisms are exposed to many different types of EDCs at any one time, each with different mechanisms of action, many of which are not fully understood at present. Most research done with EDCs has focused on the effects of these chemicals on the estrogen and thyroid systems, however, many of these same chemicals also exert strong effects on the androgen system. Also, many studies assessing the effects of EDCs on wildlife have focused on reproductive measures of exposure, often overlooking potential effects on the immune system. We have demonstrated that embryonic exposure to androgen-active EDCs, anti-androgenic p,p'-DDE and androgenic trenbolone acetate, impairs the development and function of both the immune and reproductive systems in Japanese quail. The most sensitive measured immunological target of androgen-active EDCs was the bursa of Fabricius, the primary immune organ responsible for the development of the humoral part of the immune system. Specifically, embryonic development the bursa is extremely sensitive to androgen-active EDC exposure, providing a possible mechanism for EDC-induced immunosuppression. We have also demonstrated that the bursa in Japanese quail can be resilient to embryonic exposure to EDCs, if post-hatch exposure to these chemicals is prevented. Rates to reproductive maturation and copulatory behavior were the most sensitive reproductive measures of exposure. Male and female rates to sexual maturity were altered by the one-time in ovo exposure to DDE and trenbolone. Male reproductive behavior, as measured by attempts to mount and successful cloacal contacts, was suppressed by both chemicals. The myriad of endpoints used in this study has been compiled to provide toxicologists with a list of sensitive and persistent measures that can be used as reliable biomarkers of exposure to androgen-active EDCs in birds.

Keywords

• androgen active
• endocrine disrupting chemical
• avian
• immune
• reproduction