PACAP-27 radioimmunoassay:: Description and application of a novel method

Pituitary adenylate cyclase activating polypeptide (PACAP) is a widely distributed neuropeptide that has two molecular forms with 38 and 27 amino acid residues. The aim of the present study was to develop a new, highly specific PACAP-27 assay to investigate the quantitative distribution of PACAP-27 in the central nervous system of various vertebrate species applying the same technical and experimental conditions. Our results show that the antiserum used turned to be PACAP-27 specific. The average ID50 value was 51.5 +/- 3.6 fmol/ml and the detection limit was 2 fmol/ml. PACAP-27 immunoreactivity was present in the examined brain areas, with highest concentration in the rat diencephalon and telencephalon. Swine and pigeon brain also contained significant amount of PACAP-27. Our results confirm the previously described data showing that PACAP-38 is the dominant form of PACAP in vertebrates, since PACAP-38 levels exceeded those of PACAP-27 in all examined brain areas. Furthermore, our study describes for the first time, the comparative quantitative distribution of PACAP-27 and-38 in the swine and pigeon brain.