OBJECTIVETo investigate the influences of di-2-ethylhexyl phthalate (DEHP) and its metabolite single-ethylhexyl phthalate (MEHP) on the expression of transforming growth factor-beta 1 (TGF-beta1) and telomerase activity in young male Wistar

METHODSNinety-six 2-week-old male Wistar rats were equally randomized into a normal control (NC) group, a positive control (PC) group, and six experimental groups. Those of the NC group were intragastrically administered 0.9% normal saline at a dose of 0.2 ml per kg per d for 3 weeks, those in the PC group cyclophosphamide (CTX) at 100 mg per kg per d for 1 week, and those of the experimental groups DEHP and MEHP, respectively, at a low dose (100 mg per kg per d) for 3 weeks, a moderate dose (200 mg per kg per d) for 2 weeks, and a high dose (300 mg per kg per d) for 1 week. Then we observed the morphological changes of the testicular sperm and counted the sperm heads and their abnormity rate at different doses and times. We detected the expression of TGF-beta1 in the testis tissue using immunohistochemical SABC and RT-PCR, measured the area density, and determined telomerase activity by ELISA.

RESULTSCompared with the NC group, the experimental groups showed an obvious reduction in the total sperm count and number of sperm heads (P < 0.05) and a significant increase in the rate of teratosperm (P < 0.05), such as decapitated, hookless, and double-tailed sperm. And there were no significant differences between the high-dose short-term and low-dose long-term medication groups (P > 0.05). The expression of TGF-beta1 was low in the NC group, high in the PC group, and obviously increased in the membrane and cytoplasm of spermatogenic cells of the experimental groups. The area density and TGF-beta1 mRNA expression were 0.156 0 +/- 0.003 5 and 1.51 +/- 0.20 in the NC group, 0.534 0 +/- 0.003 1 and 8.43 +/- 1.75 in the PC group, 0.289 0 +/- 0.003 6 and 3.83 +/- 1.57 in the DEHP groups, and 0.284 0 +/- 0.003 1 and 3.51 +/- 1.41 in the MEHP groups. There were significant differences between the experimental and the other two groups (P < 0.01), but not between the high-dose short-term and low-dose long-term medication groups (P > 0.05). Telomerase activity was remarkably reduced in the experimental groups as compared with the NC group (P < 0.05), but with no significant difference between the high-dose short-term and low-dose long-term medication groups (P > 0.05).

CONCLUSIONDEHP and its metabolite MEHP can evidently induce spermatogenic injury in young male rats, which may be associated with their induction of increased TGF-beta1 expression and decreased telomerase activity in the rat testis.