Glucagon and VIP in the retina.

Immunoreactive glucagon and immunoreactive vasoactive intestinal polypeptide (VIP) have been demonstrated in neuronal elements in the retina of a number of species by immunohistochemistry. In the present study, the concentrations of glucagon-like and VIP-like material in retinae from different species were determined by radioimmunoassay. The retinal concentration of glucagon-like immunoreactivity was 10-35 pg/mg in goldfish, chicken, pigeon, and frog, whereas retinae from cow, pig, rabbit, and rat contained very little. Retinae from the latter four species were on the other hand rich in VIP-like material whereas retinae from cat, guinea pig, and goldfish contained very little. The glucagon-like immunoreactive material in chicken and frog retina was subjected to gel chromatography and high performance liquid chromatography (HPLC). The results indicate that the extracted protein is of similar molecular size as porcine pancreatic glucagon, distinct from porcine glicentin. VIP immunoreactive material extracted from bovine retina was similar in molecular size as authentic porcine VIP by gel chromatography.