Chromatographic identification of Met- and Leu-enkephalin in the human fetal spinal cord

Using the indirect immunofluorescence method, enkephalin-like immunoreactivity was visualized on human fetus spinal cord sections (gestational age from 17 to 25 weeks). Immunolabeled varicose fibers and terminal-like structures were seen through the whole length fetal spinal cord principally in the dorsal gray, in the intermediate gray and in the lateral funiculus. A few enkephalin-like immunoreactive cells were sometimes detected in the intermediate gray. Finally, some immunolabeled fibers were also visible in the ventral spinal cord especially proximate to the motor nuclei areas at the sacral level. Fetal spinal cord tissue extracts from the cervical thoracic and lumbosacral region were chromatographically analyzed using high pressure liquid chromatography in combination with the radioimmunoassay. This biochemical analysis indicates that authentic pentapeptides Met- and Leu-enkephalin may account for a large part (more than 90%) of the enkephalin-like immunoreactivity detected in the fetal spinal cord investigated. Taken together our results suggest that the biosynthetic processing of Met- and Leu-enkephalin in this tissue might be functional early before birth.