These results indicated that AP1, which represents over 70 percent of the testosterone biotransformation products, is a fatty acid ester of testosterone. The esterification of testosterone to fatty acids might be a mechanism by which steroid titers are regulated and could represent a target of tributyltin toxicity. It is noteworthy that we have never, to date, detected the conversion of testosterone to estradiol by the mud snail which raises questions as to whether the inhibition of this process could possibly be the cause of elevated testosterone levels associated with imposex. Experiments are currently underway to establish relationships among tributyltin exposure, testosterone levels, testosterone-fatty acid esterification, and imposex. The following tentative results have been obtained.
Male snails have higher levels of free testosterone than do females.
The ratio of free to esterified testosterone varies in order to maintain the level of free testosterone within the sex-appropriate range. The latter two observations suggest that elevated testosterone levels may be a consequence of imposex rather than a cause of the abnormality. We postulate that imposex females have elevated testosterone levels due to the development of testosterone-producing glands. Additional Studies . Determine whether accessory male sex organs associated with imposex are responsible for the secretion of additional testosterone by these organisms.