M L Epstein — Page 5 | Search PubMed

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Multiple immunoreactive forms of met- and leu-enkephalin in fetal and neonatal rat brain and in rat gut.

We have used radioimmunoassays with carboxyl-specific antisera to study the development of met- and leu-enkephalin in rat brain and gut from 13-days of fetal age through adulthood. Fractionation of HCl extracts of fetal and neonatal brain tissues by HPLC revealed the presence of immunoreactive forms other than met- and leu-enkephalin. For example, HPLC separation of extracts of 16-day fetal brain yielded two peaks of leu-enkephalin-like immunoreactivity. One emerged at the position of leu-enkephalin, the other eluted with about one-third the retention time. There were four peaks of met-enkephalin-like immunoreactivity, one with the retention time characteristic of met-enkephalin, the others with shorter retention times. In contrast, all of the met-enkephalin-like immunoreactivity in adult brain eluted with the retention time characteristic of authentic met-enkephalin and all of the leu-enkephalin-like immunoreactivity eluted in the position of authentic leu-enkephalin. Multiple immunoreactive forms of met- and leu-enkephalin were found in extracts of both fetal and adult gut tissues.

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Development of enkephalin in the rectum and ganglion of Remak of the chick.

Radioimmunoassay (RIA) and high performance liquid chromatography were used in combination with immunocytochemistry to study the development of met-enkephalin (Met-enk) in the rectum and the ganglion of Remak of the chicken. Met-enk was detected by RIA in the rectum at 5 days of incubation (d.i.). The concentration increased from 5-9 d.i. and did not change significantly thereafter. In contrast, the concentration of Met-enk in Remak's ganglion increased throughout the developmental period of study. Met-enk immunoreactivity first appeared in cell bodies in Remak's ganglion at 6 d.i. and in a small number of processes in the wall of the rectum. By 9 d.i., Remak's ganglion contained many immunoreactive cell bodies, some of which extended processes into the wall of the rectum in the region of the myenteric plexus. Varicosities were first seen in the rectum at 13 d.i. and increased in number and staining intensity with developmental age. The fact that immunoreactive cell bodies persist in Remak's ganglion throughout the course of development and send processes into the rectum suggests that a major portion of enkephalinergic innervation of the rectum is extrinsic. On the other hand, the presence of Met-enk immunoreactivity in both nerve cell bodies and processes in rectal explants stripped of Remak's ganglion suggests that this peptide is also contained in intrinsic neurons in the chick rectum.

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