Prepubertal Di-n-Butyl Phthalate Exposure Alters Sertoli and Leydig Cell Function and Lowers Bone Density in Adult Male Mice.

Abstract

Phthalate exposure impairs testis development and function; however, whether phthalates affect nonreproductive functions is not well understood. To investigate this, C57BL/6J mice were fed 1-500 mg di-n-butyl phthalate (DBP) in corn oil, or vehicle only, daily from 4 to 14 days, after which tissues were collected (prepubertal study). Another group was fed 1-500 mg/kg·d DBP from 4 to 21 days and then maintained untreated until 8 weeks for determination of adult consequences of prepubertal exposure. Bones were assessed by microcomputed tomography and dual-energy X-ray absorptiometry and T by RIA. DBP exposure decreased prepubertal femur length, marrow volume, and mean moment of inertia. Adult animals exposed prepubertally to low DBP doses had lower bone mineral content and bone mineral density and less lean tissue mass than vehicle-treated animals. Altered dynamics of the emerging Leydig population were found in 14-day-old animals fed 100-500 mg/kg·d DBP. Adult mice had variable testicular T and serum T and LH concentrations after prepubertal exposure and a dose-dependent reduction in cytochrome p450, family 11, subfamily A, polypeptide 1. Insulin-like 3 was detected in Sertoli cells of adult mice administered the highest dose of 500 mg/kg·d DBP prepubertally, a finding supported by the induction of insulin-like 3 expression in TM4 cells exposed to 50 μM, but not 5 μM, DBP. We propose that low-dose DBP exposure is detrimental to bone but that normal bone mineral density/bone mineral content after high-dose DBP exposure reflects changes in testicular somatic cells that confer protection to bones. These findings will fuel concerns that low-dose DBP exposure impacts health beyond the reproductive axis.