IMMUNOCYTOCHEMICAL LOCALIZATION OF STANNIOCALCIN CELLS IN THE RAT-KIDNEY

Stanniocalcin (STC) is a polypeptide hormone that was first discovered in fishes, where it functions as a regulator of calcium and phosphate homoeostasis. Recently, complementary DNAs encoding human STC (hSTC) have been characterized, and recombinant hSTC has been synthesized in a bacterial expression system. In preliminary studies, STC-immunoreact ive cells have already been identified in human kidney tubules with an tibodies to recombinant hSTC. The purpose of this study was to map the overall spatial distribution of STC cells in mammalian kidney, using the rat as a model system. Immunocytochemistry was performed on fixed sections of rat kidney tissue using hSTC antiserum in conjunction with fluorescein isothiocyanate-conjugated second antibodies. STC-immunore active cells were found in cortical thick ascending limb, in macula de nsa, in distal convoluted tubules, and in the cortical and medullary c ollecting ducts. All cortical thick ascending limb cells contained imm unoreactive STC. Most distal convoluted tubules cells contained STC, a nd these were identified as principal cells. The distribution of STC c ells in cortical and medullary collecting ducts also corresponded clos ely to the known frequency of principal cells in these segments, sugge sting that principal cells are the site of STC storage and/or synthesi s in both distal convoluted tubules and collecting ducts. Some collect ing duct intercalated cells contained STC as well, and these were tent atively identified as alpha-type intercalated cells. As all tubular se gments containing STC are known to be involved in regulated ion transp ort, renally derived STC may be acting in an autocrine, paracrine and/ or endocrine fashion to regulate one or more of these transport proces ses.