Eosinophil chemotactic response to rat CGRP-1 is increased after exposure to trypsin or guinea-pig lung particulate fraction.

Calcitonin Gene-Related Peptide (CGRP) immunoreactive nerve fibres innervate the vasculature and epithelia of the peripheral airways of the guinea-pig lung. Guinea-pig eosinophils exhibit a concentration-dependent chemotactic response to rat Calcitonin Gene-Related Peptide-1 (rCGRP-1). The sequence rCGRP-1-(32-35) (valyl-glycyl-seryl-glutamic acid), which is identical to an eosinophil chemotactic factor of anaphylaxis (ECF-A) previously purified from guinea-pig lung (Goetzl, E. J. and Austen, F. (1975) Proc. Natl. Acad. Sci. USA 72, 4123-4127), was both more potent and more effective than rCGRP-1 in the chemotaxis assay. Products of rCGRP-1 tryptic digestion exhibited increased chemotactic activity compared to the intact peptide. Exposure of rCGRP-1 to a particulate fraction of guinea-pig lung also elevated its chemotactic activity, increasing the resultant potency by one hundred-fold. Resolution of pure and digested peptides by reverse-phase h.p.l.c. revealed evidence of endopeptidase activity in the lung particulate fraction. Elution times of rCGRP-1 cleavage fragments differed mostly from those of tryptic digestion.