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Effect of organotins on human aromatase activity in vitro

, : Effect of organotins on human aromatase activity in vitro. Toxicology Letters (Shannon) 126(2): 121-130, January 25th

The interaction between the human aromatase enzyme and some organotins was investigated. Tributyltin (TBT) at 12 and 59 muM and dibutyltin at 74 muM inhibited aromatase activity in vitro but monobutyltin and tri-, di- and monooctyltins were without effect. In four separate kinetic studies of aromatase, the Km(app) for testosterone was 0.24, 0.21, 0.16 and 0.24 muM. TBT inhibited aromatase activity by causing the Km(app) to be increased without affecting the Vmax, indicative of competitive inhibition. Slope and intercept replots confirmed the effect of aromatase on the Km(app). Slope replots from three separate kinetic studies provided Ki values for TBT of 64.5, 40.9 and 37.3 muM. Consequently, TBT is a competitive inhibitor of human aromatase with a Ki approximately 300-fold the Km(app) value.


DOI: 10.1016/s0378-4274(01)00451-9

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