PARENT SESSION

HP9 Endocrine Disrutpion: Steroids and Hormones
Room 12A/B, Level 4
2:10 PM - 5:30 PM, Thursday, 13 November 2003
Chair: Sibley, Paul ,

(635) Imposex snails have elevated neuropeptide hormone levels when dosed with TBT or induced in the field.

Oberdörster, E^{1, 2}, McClellan-Green, P^{2, 3}, ¹ Southern Methodist University, Dallas, TX, USA² Duke University Marine Laboratory, Beaufort, NC, USA³ North Carolina State University, Raleigh, NC, USA

ABSTRACT- 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), the combination of TBT and 500 ng 17-estradiol (E2), or vehicle (EtOH/saline) 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: Imposex was significantly induced in TBT-treated animals, whereas co-treatment with E2 reduced TBT-induced imposex. T was also able to induce imposex, but not to the extent of TBT or TBT + E2. Imposex was also dramatically and significantly induced in the transplanted animals. Male penis length followed the same pattern as female imposex development, where TBT-dosed males had significantly longer penis length than controls, E2 was able to rescue this effect, while T only marginally enhanced penis length. 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, 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.

Key words: TBT, imposex, APGWamide, gastropod