S M Samy,1,2,4 M R Fielden,1,2,4 K Chou3,4 and T R Zacharewski1,2,4

Department of Biochemistry & Molecular Biology,1 National Food Safety & Toxicology Center,2 Department of Animal Science3 and the Institute of Environmental Toxicology,4 Michigan State University, East Lansing, MI, USA

The objective of this study was to examine the effects of gestational and lactational exposure to phytoestrogen genistein on sperm quality, in vitro sperm fertilizing ability and testicular gene expression. Pregnant mice were gavaged with 0.1, 0.5, 2.5 or 10 mg/kg genistein in corn oil from gestational day (GD) 12 to postnatal day (PND) 21. Anogenital distance (AGD) of male offspring was recorded on PND 7 and PND 21. On PND 21, 105 and 315, body weight and testis weight were recorded. On PND 105 and 315, sperm count and sperm fertilizing ability of F1 males were assessed in vitro. Testicular gene expression was examined using a custom mouse cDNA microarray representing 2689 cDNA. Testicular RNA from mice in the 10 mg/kg dose group on PND 21 and 105 was compared to that from corresponding control mice. Testis weight was slightly increased in the 10 mg/kg group at PND 105 and 315 but not significantly (p>0.05). AGD was decreased on PND 21 in the 10 mg/kg dose group (p<0.05). No effect on sperm motility or sperm count was observed. In vitro fertilizing ability was significantly increased on both PND 105 (18.7%, p<0.001) and PND 315 (17.7%, p<0.001) in the 10 mg/kg group, but it was decreased by 8.5% on PND 105 in the 0.5 mg/kg dose group (p<0.05). The percent of fragmented eggs was decreased significantly on PND 105 in the 0.1, 2.5 and 10 mg/kg dose groups (p<0.001) and slightly increased on PND 315 10 mg/kg dose group. The percentage of one-cell fertilized eggs was significantly decreased on PND 315 in the 0.5, 2.5 and 10 mg/kg dose groups (p<0.001). Microarray data were analyzed using paired t-tests to identify differentially expressed genes. Five genes were under-expressed on PND 105, but there were no changes on PND 21. This study suggests that exposure to genistein in early development increases sperm fertilizing ability in adult mice.