In Vitro AR Transactivation and Binding
The ability of PZ to induce AR-mediated gene transcription was tested in MDA-kb2 cells containing endogenous human AR and stably transfected with an androgen-responsive luciferase reporter gene. Both hydroxyflutamide (1 |xM) and PZ at doses of 3 |xM or greater inhibited AR transcriptional activation induced by 0.1 nM DHT (Fig. 1A), with the effect of 1 |xM hydroxyflutamide being roughly equivalent to the effect of 10 |xM PZ. The IC50 for PZ effects on transactivation was between 3 and 10 |xM.
PZ was cytotoxic at the highest dose (100 |xM) and reduced MTT activity in MDA-kb2 cells (P < 0.001; Fig. 1B). In the competitive binding assay, increasing concentrations of PZ inhibited [3H]R1881 AR binding with an IC50 of approximately 60 |xM using cytosolic AR from rat ventral prostate tissue (Fig. 2).
Pilot Study Findings
Pilot study findings are summarized in Table 1. PZ treatment did not cause maternal death, but maternal weight gain during pregnancy was reduced in the 500 mg/kg-BW per day group (P < 0.01). There were no live births in the 500 mg/kg-BW per day group. The onset of parturition was delayed in all PZ-treated groups. Time to complete parturition was delayed up to 30 h in one of the dams that was treated with 125 mg kg-BW per day. At the same dose, another litter was entirely stillborn. Delays in delivery were associated with stillbirths at 125 and 250 mg kg-BW per day. Anogenital distance was reduced in male rat offspring at 62.5 and 250 mg/kg-BW per day and increased in females at 125 mg/kg-BW per day (significant using individual but not litter mean values).
a In contrast to the main study, the offspring data in this pilot study were analyzed using individual values as opposed to litter means, (* P s 0.05; ** P s 0.01).
b As a percentage of implantation scars. c Cleft phallus or exposed os penis.
FIG. 1. In vitro assessment of PZ effects on androgen-regulated gene transcription and cytotoxicity in MDA-kb2 cells. X-axis numbers show PZ concentrations. Media indicates cell activity with no additions. EtOH shows cell activity with ethanol vehicle control. In all other treatments, the DHT dose was 0.1 nM. FLU indicates 1 |xM hydroxyflutamide + 0.1 nM DHT. Luciferase data are expressed as fold induction over media levels. Asterisks indicate statistical difference compared to the 0 PZ (0.1 nM DHT) dose. *P < 0.05. **P < 0.001. Results are from three sets of assays run with four replicates each. Error bars = SEM. A) AR transcriptional activation. Luciferase activity, as fold induction over media, in transfected MDA cells treated with combinations of PZ and DHT. B) Cytotoxicity assessment of PZ + DHT combinations on MDA cells. Plate readings measure the conversion of MTT to formazan. Higher plate readings indicate higher numbers of live cells.