CHARACTERIZATION OF BETA-ENDORPHIN-RELATED AND ALPHA-MSH-RELATED PEPTIDES IN RAT-HEART

POMC-derived peptides and mRNA have been identified in heart tissue, a lthough POMC processing has not been fully characterized. In the prese nt study, we found that beta-lipotropin and ACTH were localized in rat heart, although they were almost entirely converted to beta-endorphin - and alpha-MSH-related peptides. Ion exchange HPLC analysis revealed that beta-endorphin(1-31) was further processed to alpha-N-acetyl-beta -endorphin(1-31), which comprised 35.9 +/- 0.1% of total immunoreactiv ity, and smaller amounts of beta-endorphin(1-27), beta-endorphin(1-26) , and their alpha-N-acetylated derivatives. The predominant alpha-MSH immunoreactive peptides coeluted with alpha-MSH and N,O-diacetyl-alpha -MSH by reverse-phase HPLC, although small amounts of ACTH(1-13)-NH2 w ere also present. Thus, multiple forms of beta-endorphin and alpha-MSH are localized in rat heart. Beta-Endorphin(1-31) is a minor constitue nt, however, indicating that nonopioid beta-endorphin peptides predomi nate.