Enzymatic activities during differentiation of the human neuroblastoma cells, LA-N-1 and LA-N-2

The presence of 10(-5) M retinoic acid (RA) in the culture medium of LA-N-1, a catecholaminergic cell line, and LA-N-2, a cholinergic cell line, enhanced their morphological differentiation. Tyrosine hydroxylase (TH) activity of the LA-N-1 cells was increased in the RA-treated cells compared with control cultures at day 4 and remained elevated. Choline acetyltransferase (ChAT) activity in the LA-N-2 cells gradually increased until 8 days in vitro (DIV) both in the untreated control and the RA treated cultures. This activity in control and treated cells decreased gradually to a constant level of activity. The ChAT activity at 8 DIV of RA-treated LA-N-2 cells was increased 2.1-fold (P less than 0.001) as compared to the control cultures. This increase in ChAT activity was accompanied by a 73% decrease of acetylcholinesterase (AChE) activity in LA-N-2 cells by 8 DIV. AChE activity of LA-N-1 cells was unchanged during the time course of the experiment. Phospholipase-A2 (PL-A2) activity in RA-treated LA-N-2 cells was increased at day 4 as compared with the control cultures. There were no differences observed in phospholipase-D (PL-D), choline kinase and GPC-phosphodiesterases activities in RA-treated and -untreated LA-N-1 and LA-N-2 cells.