SUBCELLULAR-DISTRIBUTION OF ADENOSINE-DEAMINASE AND ADENOSINE DEAMINASE-COMPLEXING PROTEIN IN RABBIT KIDNEY - IMPLICATIONS FOR ADENOSINE METABOLISM

We evaluated the age-related distribution of adenosine deaminase (ADA) and adenosine deaminase-complexing protein (CP) in rabbit kidney by i mmunohistochemical staining procedures. Paraffin- or resin-embedded ti ssue from rabbits <1 week-4 years of age were stained by the peroxidas e-anti-peroxidase (PAP) method for ADA and CP. With the exception of n eonates, the qualitative staining pattern of each protein remained gen erally constant with age. In the cortex, distal tubules, blood vessels , histiocytes, and epithelial cells lining Bowman's capsule stained fo r ADA. Proximal tubules and glomeruli were positive for CP. In contras t to the segregated pattern in the cortex, staining for ADA and CP ove rlapped in the corticomedullary junction. ADA and CP co-localized on t he brush border of tubule cells of the S3 segment. In the cytoplasm of these cells, staining for ADA was characterized by scattered punctate deposits of peroxidase reaction product. In some instances these punc tate deposits also appeared to be positive for CP. In medulla, epithel ial cells of the thin limb were positive for both ADA and CP, whereas papillary collecting ducts stained only for CP. These results document the age-related, tissue-specific expression and localization of ADA i n renal tissue, features that probably reflect the crucial role played by the enzyme in adenosine/deoxyadenosine catabolism. In addition, co localization of ADA and CP on the brush border of cells in the S3 segm ent of proximal tubules provides support for the hypothesis that one f unction of CP may be to position ADA on the plasma membrane of specifi c cell populations, further expanding the enzyme's utility in nucleosi de metabolism.