Journal Article

Testosterone-Fatty Acid Esterification: A Unique Target for the Endocrine Toxicity of Tributyltin to Gastropods1

Gerald A. LeBlanc, Meredith P. Gooding and Robin M. Sternberg

in Integrative and Comparative Biology

Published on behalf of The Society for Integrative and Comparative Biology

Volume 45, issue 1, pages 81-87
Published in print January 2005 | ISSN: 1540-7063
Published online January 2005 | e-ISSN: 1557-7023 | DOI:
Testosterone-Fatty Acid Esterification: A Unique Target for the Endocrine Toxicity of Tributyltin to Gastropods1

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Over the past thirty years, a global occurrence of sexual aberration has occurred whereby females among populations of prosobranch snails exhibit male sex characteristics. This condition, called imposex, has been causally associated with exposure to the biocide tributyltin. Tributyltin-exposed, imposex snails typically have elevated levels of testosterone which have led to the postulate that this endocrine dysfunction is responsible for imposex. This overview describes recent evidence that supports this postulate. Gastropods maintain circulating testosterone levels and administration of testosterone to females or castrates stimulates male sex differentiation in several snail species. Studies in the mud snail (Ilyanassa obsoleta) have shown that gastropods utilize a unique strategy for regulating free testosterone levels. Excess testosterone is converted to fatty acid esters by the action of a testosterone-inducible, high capacity/low affinity enzyme, acyl-CoA:testosterone acyl transferase, and stored within the organisms. Free testosterone levels are regulated during the reproductive cycle apparently due to changes in esterification/desterification suggesting that testosterone functions in the reproductive cycle of the organisms. Testosterone esterification provides a unique target in the testosterone regulatory machinery of snails that is altered by tributyltin. Indeed, imposex and free testosterone levels were elevated in field collected snails containing high tin levels, while testosterone-fatty acid ester pools were reduced in these organisms. These observations indicate that tributyltin elevates free testosterone by reducing the retention of testosterone as fatty acid-esters. This endocrine effect of tributyltin may be responsible for imposex.

Journal Article.  4141 words.  Illustrated.

Subjects: Biological Sciences

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