Synthesis of opiate peptides by a clonal pituitary tumor cell line.

Clonal mouse pituitary tumor cells, AtT-20, synthesize at least four species of peptides with opiate activity. The endorphin concentration of AtT-20 cells was estimated to be 300-600 pmol/mg of protein. The two most abundant endorphins with apparent molecular weights of 1800 and 2400 were purified 300- and 24-fold, respectively; additional minor components were found with apparent molecular weights of greater than 3000 and less than 750.