Cellular Localization of P0 (Adenine) Receptor in Rat Kidney

Abstract

P0 receptor (R) is a Gi‐coupled receptor which potentially reduces cellular cAMP levels. It binds adenine with high affinity as compared to adenosine, AMP, ADP or ATP. Hence, we localized it in rat kidney. Real‐time RT‐PCR showed highest expression of P0‐R mRNA in the superficial cortex (CTX) followed by inner and outer stripes of outer medulla (OM), deep CTX, and the base of inner medulla (IM). Immunoblots using a peptide‐derived and affinity‐purified rabbit polyclonal antibody specific for an 18‐amino acid C‐terminal sequence of rat P0‐R which we generated, detected two bands between ~36–40 kDa (MW of native protein 37 kDa) in CTX, OM and IM, which were ablated by pre‐adsorption of the antibody with the immunizing peptide. Immunoperoxidase labeling showed strongest labeling in small followed by medium blood vessels. Strong labeling is also seen in the afferent arterioles. Diffuse and weaker labeling is seen on the brush border of proximal tubules and on the medullary thick ascending limbs. Sparse labeling is seen over the peritubular interstitial cells in the CTX. Both collecting ducts (CD) and connecting tubules showed labeling, with the latter having slightly stronger intensity. In the CD the labeling is mostly on the apical aspect of the principal cells. Thus, P0‐R is expressed in vascular and tubular elements of rat kidney, and thus it may play functional roles in renal hemodynamics and transport. Funding: VA & NKF