This study aimed to investigate the effect of the widely used food emulsifier glycerin monostearate (GM) on testicular toxicity caused by the mixture of three commonly used phthalate esters (MPEs) in rats, and further to explore the underlying mechanism.

Thirty male Sprague–Dawley rats were randomly divided into three groups. Rats were orally treated with 160 mg/kg/d MPEs in the MPEs group; coinstantaneously treated with 160 mg/kg/d MPEs and 200 mg/kg/d GM in the MPEs?+?GM group; and treated with the excipient in the control group. The intervention lasted for 5 weeks. Testis weight, epididymis weight, testicular histopathology, and serum testosterone were detected for testicular toxicity evaluation. The testicular ultrastructure, the tight junction proteins zonula occluden (ZO)-1, and claudin were measured for the mechanism exploration.

The body weight, epididymis, serum testosterone level, and anogenital distance in the MPEs?+?GM group were significantly decreased compared with control group (P?<?0.05); Testicular histopathological observation showed that shed spermatids were observed in the MPEs?+?GM group. Ultrastructural observation of testicular cells showed that the cristae number was decreased in some mitochondria in the MPEs group, whereas the cristae were fused and disappeared in most mitochondria in the MPEs?+?GM group. The tight junctions were broken in the MPEs?+?GM group; meanwhile, the expression of ZO-1 and claudin were altered in the MPEs?+?GM group (P?<?0.01).

The results from this study indicated that GM aggravated MPEs’ testicular toxicity, which might relate to the injured mitochondria and damaged tight junctions in testicular tissue.