mRNA expression of zinc uptake transporters in RWPE1 and RWPE2. RWPE1 and RWPE2 were grown to ~50% confluence and treated with 0 or 75 μM ZnSO4 at 37°C for 48 hours. Cells were harvested and total RNA was isolated. Gene expression of ZIP1 and ZIP3 were measured by quantitative RT-PCR with TaqMan probes and normalized to the β-actin expression. The gene expression levels are presented as copy numbers/104 β-actin transcripts. Values are the means ± SE, n = 6 (two independent experiments).