Acute and long-term effects of in utero exposure of rats to di(n-butyl) phthalate on testicular germ cell development and proliferation

This study investigated effects of in utero exposure [embryonic day (e)13.5-e21.5] to di(n-butyl) phthalate (DBP) on fetal gonocytes and postnatal germ cell (GC) development in rats and focused on changes (delayed development) relevant to the postulated origins of human carcinoma-in situ cells. DBP treatment resulted in both early (e15.5-e17.5) and late (e19.5-e21.5) effects on gonocytes. The former involved delayed entry of proliferating gonocytes into quiescence, as indicated by prolongation/overexpression of octamer-binding transcription factor 3/4 and retinoblastoma protein phosphorylated at Ser 807/811 and Ki67 plus a 2- to 4-fold increase in gonocyte apoptosis. The late effect of DBP was to induce a greater than 10-fold increase in occurrence of multinucleated gonocytes. GC numbers in DBP-exposed males were reduced (P < 0.01) by 37, 53, 79, and 80% at e21.5 and postnatal d (d) 4, 8, and 15, respectively, with recovery to normal in scrotal testes between postnatal d 25 and 90. The DBP-induced decrease in GC numbers at d 4-8 was associated with delayed exit from quiescence, as indicated by retinoblastoma protein expression and a 28% reduction (P < 0.001) in GC proliferation index at d 6, although the latter was increased by 84% at d 25. The postnatal GC changes were associated with the early, but not late, effects of DBP on gonocytes as short-term DBP treatment from e19.5 to e20.5, induced multinucleated gonocytes as effectively as did treatment from e13.5 to e20.5, but did not reduce GC numbers on d 4. In conclusion, fetal DBP exposure delays normal GC development in both fetal (as early as e15.5) and postnatal life with the possibility of consequences for fertility.