Expression of pituitary adenylate cyclase activating polypeptide (PACAP) receptors in human glial cell tumors

Twenty-three human gliomas were analyzed: 13 astroglial neoplasms including three grade II, four grade III, and six grade IV tumors; seven ependymomas; and three oligodendrogliomas. A crude membrane fraction was prepared within 30 min after surgical removal of the tumors and was immediately tested for the presence of pituitary adenylate cyclase activating polypeptide (PACAP) receptors. PACAP stimulated adenylate cyclase activity in 23 tumors, but a specific binding of [125I-acetyl-His1]PACAP-27 was detected in only 16 tumors. In all cases, PACAP-27 and -38 were equipotent (Kd or Kact of 1-3 nM) and were 100- to 1000-fold more potent than VIP. PACAP stimulated threefold the adenylate cyclase activity in the presence of GTP. The results were compatible with an interaction of PACAP with a highly selective type I PACAP receptor and not with a high-affinity VIP/PACAP type II receptor. The presence of PACAP receptors on glial neoplasic opens the possibility of a control of the tumor growth by this family of peptides.