NEUROPEPTIDE-Y SECRETION FROM A HUMAN INSULINOMA

Neuropeptide Y (NPY) is a 36 aminoacid peptide known to inhibit glucos e-stimulated insulin secretion. NPY has been shown to be synthesized a nd secreted by rat islets of Langerhans. More recently, we described t he presence of NPY within human islets of Langerhans and in several pa ncreatic endocrine tumors. In this report, we describe the case of a p atient presenting with an insulinoma who underwent the surgical resect ion of the tumor and was studied in vivo and in vitro for NPY producti on. Using a highly specific and sensitive two-site amplified enzyme-li nked immunosorbent assay, we detected high plasma NPY levels in the pa tient prior to the surgical resection of the tumor which returned to n ormal after surgery. NPY was secreted from the tumor when kept in prim ary cell culture. Furthermore, immunohistochemistry of the insulinoma revealed the presence of NPY and its C-flanking peptide together with insulin, chromogranin and neuron specific enolase. It is concluded tha t elevated circulating NPY levels observed in this patient with an ins ulinoma reflected in vivo secretion by the tumor and it is hypothesize d that NPY could potentially be used as an endocrine marker in patient s with suspected insulinoma.