TH and neuroblastoma: We prepared cellular RNA from catecholamine-producing mouse Neuro-2a and human NB-1 neuroblastoma cells exposed to IH for 24 h, which produce catecholamines, and measured the RNA levels of tyrosine hydroxylase (Th), L-3,4-dihydroxyphenylalanine (DOPA) decarboxylase (Ddc), dopamineβ-hydroxylase (Dbh), and phenylethanolamine N-methyltransferase (Pnmt) by real-time RT-PCR.