EXPRESSION OF 2 PROOPIOMELANOCORTIN MESSENGER-RNAS IN THE ISLETS OF LANGERHANS OF NEONATAL RATS

Proopiomelanocortin-(POMC) derived peptides have been found in pituita ry and in nonpituitary tissues including the endocrine pancreas. Howev er, only a truncated 800-base POMC-like mRNA is demonstrable in most n onpituitary tissues. The functional relevance of this RNA is doubtful, because it lacks the sequences of translation initiation and signal p eptide (exon 1 and 2). Recently we have demonstrated the truncated POM C-like mRNA in pancreatic islets. Using PCR techniques in this paper w e prove the existence of a full-length POMC mRNA in this tissue, This RNA contains the sequences of exon 1 and 2, as shown by Southern blot technique and by sequencing parts of the PCR products. We suppose that this RNA is the source of the POMC peptides in islets despite of its small amount.