In vitro production and characterisation of low molecular weight forms of calcitonin gene-related peptide immunoreactivity from rat thyroid.

Rat tissues contained two forms of calcitonin gene-related peptide (CGRP) immunoreactivity of lower molecular weight than CGRP itself. Two immunoreactive products of in vitro degradation of synthetic CGRP by rat tissue homogenates were purified and shown to be chromatographically identical to these naturally occurring moieties. They reacted only with a carboxy-terminal directed CGRP antiserum indicating that they were carboxy-terminal fragments of CGRP. The larger fragment was found to have a molecular mass corresponding to amino acid residues 19-37 of the CGRP molecule.