[Demonstration of enkephalins in pheochromocytoma]

Adrenal medulla has recently been shown to contain high concentrations of enkephalin immunoreactive peptides. In the present study, we report the levels of M-ENK and L-ENK in extracts from 6 cases of human pheochromocytoma. The molecular forms of M-ENK have been characterized by gel filtration chromatography and HPLC. mRNA extracted from one tumor has been proved to code for a 80,000 kilo daltons protein containing M-ENK sequence. M-ENK immunoreactive peptides are secreted in the culture medium of dispersed cultured cells of human pheochromocytoma. This secretion is stimulated when nicotine (10(5) M) is added to the medium. However, the level of plasma M-ENK in pheochromocytoma patients is not significantly different from normal patients. Data from Holaday and al. have established that naloxone (an opiate antagonist) has a beneficial role in shock. But the origin and meaning of plasma M-ENK remain to be established.