Met-Enkephalin-Arg-Gly-Leu-Like Immunoreactivity in Adrenal Chromaefin Cells and Carotid Body Chief Cells of the Dog and Monkey

Met-Enkephalin-Arg6-Gly"'-Leu8 (Met-Enl<-Arg-Gly-Leu)-like irnmunoreactivity is shown in adrenal chromaffin cells and carotid body chief cells of the dog and monkey by immunohistochemistry using rabbit antiserum (R-0171) raised against synthetic Met-Enk-Arg-Gly-Leu conjugated with ascaris protein by the glutaraldehyde method. Immunoreactive sites were detected at the light microscopic level by the peroxidase antiperoxidase method and at the electron microscopic level by the protein Acolloidal gold method. Positive immunostaining was detected in both adrenal chromaflin cells and carotid body chief cells. The immunostaining was absorbed by preincubation of the antiserum with Met-Enl<-Arg-Gly-Leu (0.1 >< 2"6""" g/l; dilution of the antiserum, l: 4,000), whereas no absorption was observed with Leu-or Metenkephalin (50 mg/l; dilution of the antiserum, l : 4,000). Thus the present immunostaining using the R-0171 antiserum was specific to the C-terminal region of the Met-Enk-Arg-Gly-Leu molecule. In the electron microscopy, most of the imrnunoreactivity was demonstrated in the secretory granules. These results indicate that one or more Met-Enk-Arg-Gly-Leu-related peptides are contained in the carotid body as well as in the adrenal medulla.