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School of Molecular Biosciences3
College of Pharmacy,4 Center for Reproductive Biology, Washington State University, Pullman, Washington 99164
Phthalates have been shown to elicit contrasting effects on the testis and the liver, causing testicular degeneration and promoting abnormal hepatocyte proliferation and carcinogenesis. In the present study, we compared the effects of phthalates on testicular and liver cells to better understand the mechanisms by which phthalates cause testicular degeneration. In vivo treatment of rats with di-(2-ethylhexyl) phthalate (DEHP) caused a threefold increase of germ cell apoptosis in the testis, whereas apoptosis was not changed significantly in livers from the same animals. Western blot analyses revealed that peroxisome proliferator-activated receptor (PPAR)
is equally abundant in the liver and the testis, whereas PPAR
and retinoic acid receptor (RAR)
are expressed more in the testis. To determine whether the principal metabolite of DEHP, mono-(2-ethylhexyl) phthalate (MEHP), or a strong peroxisome proliferator, 4-chloro-6(2,3-xylindino)-2-pyrimidinylthioacetic acid (Wy-14,643), have a differential effect in Sertoli and liver cells by altering the function of RAR
and PPARs, their nuclear trafficking patterns were compared in Sertoli and liver cells after treatment. Both MEHP and Wy-14,643 increased the nuclear localization of PPAR
and PPAR
in Sertoli cells, but they decreased the nuclear localization of RAR
, as previously shown. Both PPAR
and PPAR
were in the nucleus and cytoplasm of liver cells, but RAR
was predominant in the cytoplasm, regardless of the treatment. At the molecular level, MEHP and Wy-14,643 reduced the amount of phosphorylated mitogen-activated protein kinase (activated MAPK) in Sertoli cells. In comparison, both MEHP and Wy-14,643 increased phosphorylated MAPK in liver cells. These results suggest that phthalates may cause contrasting effects on the testis and the liver by differential activation of the MAPK pathway, RAR
, PPAR
, and PPAR
in these organs.
2 Correspondence: Kwan Hee Kim, School of Molecular Biosciences, Washington State University, Pullman, WA 99164-4234. FAX 509 335 1907; khkim{at}wsu.edu
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