PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE VASOACTIVE INTESTINAL POLYPEPTIDE RECEPTOR SUBTYPES ARE DIFFERENTLY EXPRESSED IN RAT TRANSPLANTED PITUITARY-TUMORS (SMTTW) AND IN THE NORMAL GLAND/

The expression of the pituitary adenylate cyclase-activating polypepti de/vasoactive intestinal polypeptide (PACAP/VIP) receptor subtypes was evaluated in the normal rat pituitary gland and in different rat spon taneous transplantable SMtTW tumours (SMtTW(2) which expresses prolact in (PRL), SMtTW(10) which expresses GH and SMtTW, which expresses both PRL and GH) by measurement of PACAP/VIP-stimulated adenylate cyclase activity and detection of the presence of mRNA coding for the differen t receptor forms. In normal glands, the order of potency of the peptid es suggested that adenylate cyclase activity was mediated through inte raction with PACAP selective receptors (PACAP I receptors); mRNAs codi ng for the PACAP I receptor, but also for the PACAP II VIP2 receptor, were detected. In SMtTW(2) tumours, the functional response was close to that observed in the presence of PACAP II VIP2 receptors; mRNAs cod ing for PACAP I and PACAP II VIP1 and PACAP II VIP2 receptors were det ected. In the SMtTW(10) tumours, the functional response was complex b ut compatible with the involvement of PACAP I and PACAP II receptors; mRNAs coding for the PACAP I and PACAP II VIP1 receptors were detected . Thus, while the control of normal pituitary gland adenylate cyclase activity by PACAP and VIP was mediated by PACAP-selective receptors, i n spontaneous transplantable tumours a variable profile was observed a nd PACAP, as well as VIP1 and VIP2 receptors, may contribute to the re sponses.