Gene and cDNA cloning and characterization of the mouse V3/V1b pituitary vasopressin receptor

The gene of the mouse V3/V1b receptor was identified by homology cloning. O ne of the genomic clones contained the entire coding sequence. The cDNA pre sented high identity with rat (92%) and human (84%) sequences. Southern blo t analysis indicated the existence of a single gene. Tissue distribution wa s studied by RT-PCR. The major site of expression was the pituitary. A fain t signal was also present in hypothalamus, brain, adrenal, pancreas and col on. The mouse corticotroph cell line, AtT20, did not express the transcript . In order to confirm the identity of the sequence, the V3/V1b receptor cDN A was cloned and stably expressed in CHO-AA8 Tet-Off cells under the contro l of tetracycline. When transfected cells were treated with arginine vasopr essin (AVP), inositol phosphate production increased in a dose-dependent ma nner, indicating that the V3/T1b receptor couples to phospholipase C. Moreo ver, AVP did not stimulate cAMP production. Binding studies with [H-3]AVP i ndicated that the affinity of the mouse V3/V1b receptor (K-d=0.5 nM) is sim ilar to that reported for rat and human receptors. The rank order of potenc y established in competition binding experiments with different analogues w as representative of a V3/V1b profile, distinct from V1a and V2. However, s ignificant differences were found between human and mouse receptors tested in parallel. Thus the pharmacology of V3/V1b receptors can not be transpose d among different species.