Time-Dependent and Compartment-Specific Effects of In Utero Exposure to Di(n-butyl) Phthalate on Gene/Protein Expression in the Fetal Rat Testis as Revealed by Transcription Profiling and Laser Capture Microdissection

Abstract

We undertook transcription profiling of fetal testis RNA on gestational days e15.5, 17.5, and 19.5 in offspring from dams treated daily from e12.5 with 500 mg/kg di(n-butyl) phthalate (DBP). At e17.5-19.5, reduced expression of genes involved in cholesterol uptake/metabolism and steroidogenesis was identified in DBP-exposed animals, including scavenger receptor B1 (SCARB1), HMGCoA synthase, steroidogenic acute regulatory protein, Cyp11a, and Cyp17. Genes encoding inhibin-alpha, phosphatidylethanolamine-binding protein (PEBP), and cellular retinoic acid-binding protein 2 (CRABP2) were also downregulated. Most of the aforementioned genes are regulated by steroidogenic factor 1 (SF1) but no consistent change in SF1 mRNA or protein expression was detected. Expression of the aforementioned genes was unaffected at e15.5, but expression of other genes was significantly altered (mostly upregulated). To gain further insight, RNA from interstitial (INT) and seminiferous cord (CORD) tissue obtained by laser capture microdissection (e19.5) was used for transcription profiling. This confirmed most gene expression changes identified for whole testes, but some were remarkably compartment specific. Inhibin-alpha, PEBP, and CRABP2 gene expression were all downregulated in INT but not in CORD, as confirmed by immunohistochemistry; similarly, SCARB1 was downregulated 4.6-fold in INT but only 2.3-fold in CORD. DBP-induced gene expression changes specific to CORD involved small magnitude (less than twofold) reductions or upregulation. These results extend earlier findings and point to the Leydig cells as a primary target of DBP-induced dysfunction. The observed gene expression changes, and their compartmentalization, suggest a possible role for peroxisome proliferator-mediated alteration of cofactor availability as a mechanism underlying DBP-induced Leydig cell dysfunction.