OBJECTIVETo investigate the effect of in utero exposure to di-n-butyl phthalate (DBP) on the protein expression in the penile tissue of hypospadiac rats, isolate and identify differentially expressed proteins, and determine the role of the differential expression of Annexin A3 in the development of hypospadia in the rat offspring after maternal exposure to DBP.

METHODSTwenty pregnant SD rats were randomly assigned to an experimental group, intragastrically administered DBP at 800 mg/kg, and a control group, given soybean oil at 5 ml/kg, both for 5 days. Three days after birth, the penises of the newborn rats were removed, and the total protein extracted for 2D-electrophoretic separation and image analysis. Differentially expressed protein spots were screened and identified by mass spectrometry, and the changes in the expression of Annexin A3 detected by Western blotting and immunohistochemistry.

RESULTSThirty-one differentially expressed protein spots were screened, of which 17 were identified by mass spectrometry and the SwissProt database, including pyruvate kinase M2, alpha-enolase, and Annexin A3. Western blot showed that Annexin A3 was mainly located in the urethral epithelia and had a lower expression in the hypospadiac rats (1.851 +/- 0.014, n = 10) than in the controls (2.603 +/- 0.012, n = 10) (P < 0.05).

CONCLUSIONA pedigree of differentially expressed proteins in the penises of DBP-induced hypospadia and normal rats was established by the proteomic method. The differential expression of Annexin A3 may play an important role in the development of hypospadia.