Nerve growth factor induces specific enkephalin binding sites in a nerve cell line

Specific enkephalin binding was found in a rat pheochromocytoma cell line, PC12 (subclone h), when cultured in the presence of nerve growth factor (NGF; 50 ng/ml). Specific binding of [3H][D-Ala2]Met-enkephalinamide was saturable with a KD=2.4 nM and Bmax = 866 fmol/mg of protein. The binding was displaced completely by morphine and naloxone at a concentration of 10(-4) and 10(-6) M, respectively. beta-Endorphin and dynorphin [1-13] also displaced the binding; KI = 9.6 and 81.6 nM, respectively. Enkephalin binding in PC12h cells cultured in the absence of NGF was very low. Binding was dramatically increased when cultured in the presence of NGF for 7 to 10 days. The enkephalin binding was induced by NGF in the cells cultured in a hormone-supplemented serum-free medium. In contrast, epidermal growth factor was of two orders lower potency, and insulin had no effect on the expression of enkephalin binding sites. Since the differentiation effects of NGF on PC12h cells are though to offer a model system to investigate the effect of NGH on neurons, the present observations may suggest a physiological role for NGF in the induction and maintenance of specific opiate receptors during development of the autonomic nervous system.