The neuropeptide hormone APGWamide is elevated in imposex snails dosed with TBT or collected from the field

We have shown that the peptide hormone APGWamide may be involved in TBT-induced imposex in mud snails. The goal of this study was to further investigate endogenous APGWamide levels in imposex snails or TBT-exposed snails. Snails were collected from a relatively pristine Estuarine Reserve, and were injected S.Q. with either 20 ng TBT, 500 ng testosterone (T), or vehicle (EtOH) controls. In addition, snails were caged for three months in a site which historically has 100% imposex females and males without regressing sex organs. Endogenous APGWamide immuno-reactivity was measured in snail body homogenates via Western blotting and compared to purified APGWamide standard. Results: Control males had significantly higher APGWamide levels than control females. Male normalized penis length was highly correlated to endogenous APGWamide levels (r2 = 0.475). All TBT-treated animals, whether male, female, or imposex, had levels of APGWamide similar to control males and significantly higher than control females. In T treated animals, APGWamide levels were identical to the corresponding vehicle controls, 0141-1136/$ - see front matter 2004 Published by Elsevier Ltd. doi:10.1016/j.marenvres.2004.03.110 www.elsevier.com/locate/marenvrev Marine Environmental Research 58 (2004) 407–418 MARINE ENVIRONMENTAL RESEARCH e.g., females had similar levels to control females. Since extremely high doses of T can induce imposex, but APGWamide levels are not elevated, it is possible that T interferes with a downstream signaling event. For the transferred animals, both males and females had significantly higher levels of APGWamide than their respective controls. In summary, endogenous APGWamide is significantly elevated in snails that are either dosed with TBT or that are re-located to sites with historically high imposex levels. This research was funded by an EPA STAR grant #R827401