TY - JOUR
T1 - Metabolism of tamoxifen and its uterotrophic activity
AU - Lyman, Stewart D.
AU - Craig Jordan, V.
N1 - Funding Information:
One possible explanation for the disparate action of tamoxifen in these species would be the differential formation in mice, rats, and chickens, of tamoxifen metabolites that have different estrogenic or antiestrogenic properties. Tamoxifen is anti-estrogenic in a cell culture system in which no metabolism of this compound occurs \[6\],s uggesting that the antiestrogenic properties of this drug are not dependent on its metabolism. The dimethylaminoethyl portion of the tamoxifen side chain is necessary for its antiestrogenic properties in the rat uterus; * A portion of this work was presented at the 1984 FASEB meeting, St. Louis, MO. t Supported by NIH Grant PO1-20432 awarded to the Wisconsin Clinical Cancer Center and by U.S. Public Health Service Grant CA 32713. S.D.L. is a graduate student of the McArdle Laboratory for Cancer Research, University of Wisconsin. § To whom all reprint requests should be sent.
PY - 1985/8/1
Y1 - 1985/8/1
N2 - Tamoxifen is an estrogen agonist in mouse uterus, a partial estrogen agonist/antagonist in rat uterus, and a pure estrogen antagonist in chicken oviduct. Tamoxifen metabolism was examined both in vitro and in vivo to determine if differences in the species response to this drug resulted from the differential formation of metabolites with estrogenic or antiestrogenic activity. Animals were given a subcutaneous injection of [3H]tamoxifen, and 4 or 24 hr later tamoxifen and its metabolites were extracted from tissues and separated by TLC. The profiles of metabolites extracted from livers of these species were qualitatively similar; the principle metabolite was 4-hydroxytamoxifen, which comprised 27, 14, and 16% of the radioactivity from mouse, rat, and chicken livers, respectively, at 24 hr. Tamoxifen, however, was the principal compound extracted from all three livers. Metabolites extracted from mouse and rat uteri were the same ones obtained from liver, although their abundance (relative to tamoxifen) was much lower in uteri than in liver. Metabolite E and bisphenol, two tamoxifen derivatives that we believed might account for the uterotrophic effect of tamoxifen in the mouse, were found not to be formed in either liver or uterus. Tamoxifen metabolism was also studied in vitro using liver microsomes from these same species; The same metabolites were formed in vitro as in vivo, although their relative abundances were lower in vitro. No clear-cut differences in metabolism were seen that would account for the disparate pharmacological effects of tamoxifen in these species.
AB - Tamoxifen is an estrogen agonist in mouse uterus, a partial estrogen agonist/antagonist in rat uterus, and a pure estrogen antagonist in chicken oviduct. Tamoxifen metabolism was examined both in vitro and in vivo to determine if differences in the species response to this drug resulted from the differential formation of metabolites with estrogenic or antiestrogenic activity. Animals were given a subcutaneous injection of [3H]tamoxifen, and 4 or 24 hr later tamoxifen and its metabolites were extracted from tissues and separated by TLC. The profiles of metabolites extracted from livers of these species were qualitatively similar; the principle metabolite was 4-hydroxytamoxifen, which comprised 27, 14, and 16% of the radioactivity from mouse, rat, and chicken livers, respectively, at 24 hr. Tamoxifen, however, was the principal compound extracted from all three livers. Metabolites extracted from mouse and rat uteri were the same ones obtained from liver, although their abundance (relative to tamoxifen) was much lower in uteri than in liver. Metabolite E and bisphenol, two tamoxifen derivatives that we believed might account for the uterotrophic effect of tamoxifen in the mouse, were found not to be formed in either liver or uterus. Tamoxifen metabolism was also studied in vitro using liver microsomes from these same species; The same metabolites were formed in vitro as in vivo, although their relative abundances were lower in vitro. No clear-cut differences in metabolism were seen that would account for the disparate pharmacological effects of tamoxifen in these species.
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U2 - 10.1016/0006-2952(85)90580-5
DO - 10.1016/0006-2952(85)90580-5
M3 - Article
C2 - 4015715
AN - SCOPUS:0021889085
SN - 0006-2952
VL - 34
SP - 2787
EP - 2794
JO - Biochemical Pharmacology
JF - Biochemical Pharmacology
IS - 15
ER -