OBERD�RSTER, E; MCCLELLAN-GREEN, P; Southern Methodist University and Duke University Marine Laboratory; N.C. State University and Duke University Marine Laboratory, Beaufort, NC: Expression of the peptide hormone APGWamide in imposex and normal snails: A neurotoxicity mechanism for imposex induction.

The environmental contaminant tributyltin (TBT), induces female neogastropods to grow male accessory sex organs. This condition is termed imposex, and has been shown in numerous species world wide. Although the initial focus for the mechanism of this condition was on the steroid hormone system, it has become clear that a neuroendocrine pathway is involved in inducing imposex. We have shown that an exogenously administered peptide hormone, APGWamide, induces imposex in mud snail, Ilyanassa obsoleta. Others have since shown that APGWamide is effective in imposex induction in other gastropod species. In this study, we examined endogenous APGWamide levels in imposex snails or TBT-exposed snails. Snails from a relatively pristine area 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 ELISA and compared to purified APGWamide standard. Control males had significantly higher APGWamide levels than control females, and all TBT-treated animals, whether male, female, or imposex, had elevated levels of APGWamide. In T treated animals, APGWamide levels were identical to the corresponding vehicle controls. 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, males, normal females and imposex females had significantly elevated levels of APGWamide. This research was funded by an EPA STAR grant #R827401-01.