IMMUNOLOCALIZATION OF V-1 VASOPRESSIN RECEPTORS IN THE RAT-KIDNEY USING ANTIRECEPTOR ANTIBODIES

By using immunocytochemical techniques we have been able to localize t he V-1 vasopressin receptor in the rat kidney. Immunoblotting using an antiserum raised against an affinity-purified vasopressin receptor sh owed a 55,000 daltons protein band that has a molecular mass similar t o that of the liver V-1 vasopressin receptor, as demonstrated by cross -linking studies. Immunoblotting of the antibody showed a band of 55,0 00 daltons in A-10 cells, which contains the V-1 subtype, whereas it d id not stain LLC-PK1 cells, which possess the V-2 subtype, showing tha t the antibody recognizes the V-1 vasopressin receptor. The immunostai ning of kidney sections with this antiserum showed a strong reaction o f the connecting tubules and cortical and medullary collecting ducts. The immunostaining pattern of connecting tubule and collecting duct ce lls was different, that is, the former showed a staining of both the a pical and basal plasma membrane but also in the cytoplasm, whereas the latter showed a strong reaction mainly in the basolateral membrane. I mmunostaining of consecutive serial sections with an antiserum raised against tissue kallikrein, an enzyme present exclusively in connecting tubules, and with the anti-receptor serum allowed us to show, for the first time, the presence of the vasopressin receptor in the connectin g tubule cells and their absence in intercalated cells, the other cell type present in connecting tubules. These findings support experiment s carried in the eighties on the release of renal tissue kallikrein by AVP.