Diisobutyl phthalate has comparable anti-androgenic effects to di-n-butyl phthalate in fetal rat testis.
Phthalates are widely used as plasticizers in various consumer products and building materials. Some of the phthalates are known to interfere with male reproductive development in rats, and di-n-butyl phthalate (DBP), diethylhexyl phthalate (DEHP) and butyl benzyl phthalate (BBP) were recently banned for use in toys in the EU mainly due to their reproductive toxicity. Diisobutyl phthalate (DiBP) has similar structural and application properties as DBP, and is being used as a substitute for DBP. However, knowledge on male reproductive effects of DiBP in experimental animals is lacking.


METHODS
In the current study, four groups of pregnant Wistar rats were exposed to either 0mg/kg bw/day or 600 mg/kg bw/day of DiBP from gestation day (GD) 7 to either GD 19 or GD 20/21. Male offspring was examined at GD 19 or GD 20/21 for effects on testicular testosterone production and testicular histopathology. Changes in anogenital distance (AGD) were evaluated as an indication of feminisation of males.


RESULTS
Anogenital distance was statistically significantly reduced at GD 20/21 together with reductions in testicular testosterone production and testicular testosterone content. Histopathological effects (Leydig cell hyperplasia, Sertoli cell vacuolisation, central location of gonocytes and presence of multinuclear gonocytes) known for DBP and DEHP were observed in testes of DiBP-exposed animals at GD 20/21. Additionally, immunohistochemical expression of P450scc and StAR proteins in Leydig cells was reduced by DiBP. At GD 19, these effects on anogenital distance, testosterone levels and histopathology were less prominent.


CONCLUSIONS
In this study, GD 20/21 rather than GD 19 appears to be the optimal time for investigating changes in anogenital distance, testosterone levels, and testicular histopathology. DiBP has similar testicular and developmental effects as DBP and DEHP, and although more developmental and especially postnatal studies are needed to clearly identify the reproductive effects of DiBP, this study indicates a reason for concern about the use of DiBP as a substitute for DBP.
Borch
Julie
J
Danish Institute for Food and Veterinary Research, Mørkhøj Bygade 19, DK-2860 Søborg, Denmark.
Axelstad
Marta
M
Vinggaard
Anne Marie
AM
Dalgaard
Majken
M
D000726:Androgen Antagonists / Q000633:toxicity*; D000818:Animals; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D003993:Dibutyl Phthalate / Q000031:analogs & derivatives* / Q000633:toxicity; D005260:Female; D047109:Fetal Development / Q000187:drug effects* / Q000502:physiology; D005333:Fetus / Q000166:cytology / Q000187:drug effects* / Q000473:pathology; D007150:Immunohistochemistry; D007985:Leydig Cells / Q000166:cytology / Q000502:physiology; D008297:Male; D018811:Maternal Exposure; D010968:Plasticizers / Q000633:toxicity*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D012708:Sertoli Cells / Q000166:cytology / Q000502:physiology; D013737:Testis / Q000166:cytology / Q000187:drug effects* / Q000196:embryology / Q000473:pathology; D013739:Testosterone / Q000378:metabolism
D000726:Androgen Antagonists; D010968:Plasticizers; D003993:Dibutyl Phthalate; D013739:Testosterone; C025605:diisobutyl phthalate