Differential loss of biological activity of the enkephalins induced by current.

Passage of current across solutions of enkephalins caused loss of biological activity of the peptides, this loss increasing as current strength was increased. The presence of a vas deferens tissue prevented the current-induced loss of activity of Leu-enkephalin but had no effect on the loss of activity of Met-enkephalin. These results provide a possible explanation for the differential potency of the enkephalins on the vas and provide a reason for the inability of several laboratories to show electrically induced enkephalin release.