Comparative Cytotoxicity and Sperm Motility Using a Computer-Aided Sperm Analysis System (CASA) for Isomers of Phthalic Acid, a Common Final Metabolite of Phthalates

Abstract

The general population is exposed to phthalates through consumer products, diet, and medical devices. Phthalic acid (PA) is a common final metabolite of phthalates, and its isomers include isophthalic acid (IPA), terephthalic acid (TPA), and phthalaldehyde (o-phthalic acid, OPA). The purpose of this study was to investigate whether PA and PA isomers exert reproductive toxicity, including altered sperm movement. In vitro cell viability assays were comparatively performed using Sertoli and liver cell lines. In animal experiments, PA or PA isomers (10, 100, or 1000 mg/kg) were administered orally to Sprague-Dawley (SD) rats, and semen samples were analyzed by computer-aided sperm analysis (CASA). PA treatment produced a significant effect on curvilinear velocity (VCL), straight-line velocity (VSL), mean velocity or average path velocity (VAP), amplitude of lateral head displacement (ALH), and frequency of head displacement or beat cross-frequency (BCF), whereas IPA, TPA, and OPA induced no marked effects. In vitro cell viability assays showed that mouse normal testis cells (TM4) and human testis cancer cells (NTERA 2 cl. D1) were more sensitive to PA and OPA than mouse liver normal cells (NCTC clone 1469) and human fetal liver cells (FL 62891). Our study suggests that PA and PA isomers specifically produced significant in vitro and in vivo reproductive toxicity, particularly sperm toxicity and testis cell cytotoxicity. Of the isomers examined, PA appeared to be the most toxic and may serve as a surrogate biomarker for reproductive toxicity following mixed exposure to phthalates.