Inhibition of testicular steroidogenesis by the xenoestrogen bisphenol A is associated with reduced pituitary luteinizing hormone secretion and decreased steroidogenic enzyme gene expression in rat Leydig cells
Exposure of humans to bisphenol A (BPA), a monomer in polycarbonate plastics and a constituent of resins used in food packaging and dentistry, is significant. In this report exposure of rats to 2.4 μg/kg·d (a dose that approximates BPA levels in the environment) from postnatal d 21-35 suppressed serum LH (0.21 ± 0.05 ng/ml; vs. control, 0.52 ± 0.04; P < 0.01) and testosterone (T) levels (1.62 ± 0.16 ng/ml; vs. control, 2.52 ± 0.21; P < 0.05), in association with decreased LHβ and increased estrogen receptor β pituitary mRNA levels as measured by RT-PCR. Treatment of adult Leydig cells with 0.01 nM BPA decreased T biosynthesis by 25% as a result of decreased expression of the steroidogenic enzyme 17α-hydroxylase/ 17-20 lyase. BPA decreased serum 17β-estradiol levels from 0.31 ± 0.02 ng/ml (control) to 0.22 ± 0.02, 0.19 ± 0.02, and 0.23 ± 0.03 ng/ml in rats exposed to 2.4 μg, 10 μg, or 100 mg/kg·d BPA, respectively, from 21-35 d of age (P < 0.05) due to its ability to inhibit Leydig cell aromatase activity. Exposures of pregnant and nursing dams, i.e. from gestation d 12 to postnatal d 21, decreased T levels in the testicular interstitial fluid from 420 ± 34 (control) to 261 ± 22 (P < 0.05) ng/ml in adulthood, implying that the perinatal period is a sensitive window of exposure to BPA. As BPA has been measured in several human populations, further studies are warranted to assess the effects of BPA on male fertility.
Akingbemi, Benson T., Chantal M. Sottas, Anna I. Koulova, Gary R. Klinefelter, and Matthew P. Hardy. 2004. "Inhibition of testicular steroidogenesis by the xenoestrogen bisphenol A is associated with reduced pituitary luteinizing hormone secretion and decreased steroidogenic enzyme gene expression in rat Leydig cells," Endocrinology 145(2): 592–603.