PIGS PRODUCE ONLY A SINGLE FORM OF CGRP, PART OF WHICH IS PROCESSED TO N-TERMINAL AND C-TERMINAL FRAGMENTS

Using radioimmunoassays with two different antisera, one directed towa rds the C-terminal and one towards the mid part of porcine and human a lpha-CGRP, respectively, we isolated three immunoreactive peptides fro m acid/ethanol extracts of porcine spinal ford by means of HPLC. By am ino acid sequence analysis and mass spectrometry (PDMS), the most abun dant peptide was found to be identical to the 37 residue CGRP previous ly isolated from porcine adrenal glands and spinal cord. The two remai ning peptides were identified as pCGRP(18-37) and pCGRP(19-37). Furthe rmore, the oxidized forms (oxidized Met in position 22) of all three p eptides were isolated. We extracted a large amount of tissue and the e xtractable peptides were purified without discarding side fractions. T he purification steps were monitored by immunochemical methods that ar e highly sensitive for human alpha- and beta-CGRP. Yet we were unable to detect any second full-length form of CGRP. Thus, we conclude that only a single form of full-length CGRP is found in pigs and that this peptide may be cleaved to produce potentially bioactive N- and C-termi nal fragments.