Production and regulation of enkephalin-like peptides in neuroblastoma x glioma cells.

Partially purified extracts from neuroblastoma x glioma hybrid cells inhibit via opioid receptors the PGE1-elicited formation of cyclic AMP in the same hybrid cell system. The purification of extracts reveals two active fractions very similar to Met- and Leu-enkephalin by several criteria including treatment with cyanogen bromide. On an average, the intracellular concentration of opioids in hybrid cells is 0.1 pmol per mg protein. The concentration is strongly dependent on the cell density. Furthermore, the content in the hybrids of enkephalin-like peptides is specifically elevated by glucocorticoids.