Vasoactive intestinal polypeptide (VIP) in epithelial cells of the gut mucosa of an elasmobranchian cartilaginous fish, the ray.

As part of study of the phylogeny of VIP, it was observed that the colonic mucosa of the cartilaginous fish, Raja radiata and Raja clavata, contained numerous epithelial cells, obviously of closed type, displaying intense VIP immunoreactivity. Accordingly, high concentrations of VIP were found by radioimmunoassay. At the ultrastructural level, the VIP cells were characterized by the presence of highly electron dense secretory granules. The colonic mucosa of the ray may be a good source for the isolation of an early VIP.