β-ENDORPHIN IN THE BRAIN AND PITUITARY; EVIDENCE FOR TWO SPECIFIC PROCESSING PATTERNS

Peptides related to β-endorphin (residues 1–31)were extracted from rat pituitary and brain, resolved by chromatography and determined by RIA. In the pituitary, the biologically potent form of β-endorphin was the major immunoreactive peptide in the anterior region while the inactive acetylated forms of β-endorphin and C′-fragment (residues 1–27 and 1–26) were the major peptides of the pars intermedia. In the brain, the biologically potent form of β-endorphin was present in the hypothalamus as the major immunoreactive peptide; in the amygdala and mid brain it was accompanied by des histidine C′-fragment (β-endorphin 1–26). In the hippocampus, colliculae and brain stem, N-acetylated forms of the β-endorphin related peptides, which are inert as opiates, predominated. The results demonstrate the existence in these tissues of two distinct mechanisms for processing of the C-terminal region of the ACTH-endorphin prohormone.