Submission Number: BEN-4-34-21

Abstract Number: 453

GESTATIONAL AND PUBERTAL EXPOSURE TO DIETHYLHEXYLPHTHALATE IN VIVO DECREASES TESTOSTERONE BIOSYNTHESIS BY RAT LEYDIG CELLS.

BT Akingbemi* ¹, Gary R Klinefelter* ² and MP Hardy* ¹

Center for Biomedical Research, Population Council, New York, NY ¹
U.S.EPA, NHEERL, Reproductive Toxicology Division, Research Triangle Park, NC ²

Abstract:
Diethylhexylphthalate (DEHP) is the most widely used plasticizer in the food and construction industries, and is known to have adverse effects on male fertility. In rodents, Sertoli cell dysfunction results from exposure to DEHP, with a consequent reduction in the rate of spermatogenesis. It is unclear, however, whether the effects of DEHP result from direct action on Sertoli cells or indirectly through changes in the level of androgen stimulation when exposure to this compound is prenatal or pubertal. Therefore, we conducted experiments to compare Leydig cell testosterone biosynthesis after male rats were exposed to DEHP at two different time periods: in utero, and in the postnatal period. Pregnant Long-Evans dams were gavaged with 100 mg DEHP per kilogram (KG) of body weight (BW) from gestation days 12 to 20. At postnatal day (PND) 21 (n = 18), serum T was reduced in DEHP-treated rats compared to control, 1.8 0.07 vs 2.6 0.06 ng/ml. Serum LH was also decreased (0.11 0.01 vs 0.26 0.10; p < 0.01). Leydig cells from treated rats had lower rates of T production in vitro than control: basal T production was 0.4 0.02 vs 0.7 0.04, and LH-stimulated (100 ng/ml) production was 0.7 0.05 vs 1.6 0.15 ng/10⁶ cells 3 h^-1 (p < 0.01). At PND 35 (n = 10), the serum levels of T remained lower in DEHP-treated rats (1.8 0.18 ng/ml) compared to control (3.7 0.2), in parallel with LH values (DEHP, 0.3 0.06 and control, 0.5 0.07; p < 0.01). However, these parameters did not differ in treated rats (n = 9) that were evaluated at 90 days of age. To assess the effects of postnatal exposure, pubertal rats (n = 10) were gavaged with 0, 1, 10, and 100 mg/KG/BW DEHP for 14 days, from PND 21 to 34, and sacrificed on PND 35. This dosage regimen did not affect serum T and LH, but basal T production by Leydig cells was reduced at 100 mg (DEHP, 5.2 0.2 and control, 8.1 0.6, ng/10⁶ cells 3 h^-1, p < 0.01). These observations suggest that DEHP may exert differential effects on T biosynthesis in developing Leydig cells through: 1) suppression of pituitary gonadotropin secretion (e.g., prenatal exposure); and 2) direct action on Leydig cells as evidenced by altered T production rates in vitro (e.g., pre- and postnatal exposure). Future studies will determine whether these developmental alterations in T production result in reduced fertility in adulthood. Supported by NIEHS grant # ES 10233. .

Keywords: Leydig cells, testosterone, toxicology

This abstract is being presented at: 2:00 PM in session:
SESSION 19: ENDOCRINE DISRUPTION