Selection for Neuroblastoma Cells that Synthesize Certain Transmitters

A selection procedure was devised for neurons and related cells that depends upon the ability of the cells to synthesize certain amine neurotransmitters. The rationale for selection is that tyrosine is an essential amino acid for most mammalian cells and that three enzymes from mammalian sources can catalyze the synthesis of tyrosine: phenylalanine hydroxylase (EC 1.14.16.1), tyrosine hydroxylase (EC 1.14.16.2), and tryptophan hydroxylase (EC 1.14.16.4). Tyrosine hydroxylase is found predominantly in adrenergic neurons and related cells that synthesize dopamine, norepinephrine, and epinephrine, and tryptophan hydroxylase in cells synthesizing serotonin or melatonin. Only 1 out of 70,000 uncloned mouse neuroblastoma cells grew well in the absence of tyrosine. Approximately 50% of the cell lines obtained by selection had tyrosine hydroxylase activity. This selection procedure thus provides a simple means of obtaining cell lines of neural origin on the basis of their ability to synthesize putative transmitters.