Fig. 9. RACK-I siRNA blocks the TPA-induced increase in tyrosinase activity. Paired melanocyte cultures were transfected with 10 nM control RNA or siRNA and 72 hours after transfection cells were treated with 10^–7 M TPA or vehicle alone for 90 minutes. Then cells were harvested and tyrosinase activity was measured. Statistical analysis using a paired Student's t-test was performed.