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.