S100-like protein in the goldfish (Carassius auratus) kidney - An immunohistochemical study

The presence and distribution of S100-like protein in the goldfish (Carassi us auratus L.) kidney has been studied by the use of immunohistochemical an d histochemical methods. Simple immunohistochemistry (peroxidase anti-perox idase method) was carried out with a polyclonal antibody against a mixture of both S100 alpha and S100 beta proteins. In order to confirm the cell-typ e containing S-100-like immunoreactivity, the colocalization of S-100-like protein immunoreactivity with periodic acid-Schiff (PAS) reaction was inves tigated by using double staining with indirect immunofluorescence and PAS h istochemistry. S100-like immunoreactivity was detected only in juxtaglomeru lar cells located in the renal arterial branch and never on afferent arteri oles. No immunoreactivity was observed in other tracts of the nephron or in the interstitial cells. Double staining confirmed that S-100-like immunore activity and PAS reactivity were colocalized in juxtaglomerular cells. Thes e findings are the first regarding the presence and distribution of S100-li ke protein in the teleost kidney; they add a new member to the list of extr a-neural S100-like-containing cell types and confirm that the antigen canno t be regarded as nervous-system-specific. In addition, a concentration of S 100-like immunoreactivity in juxtaglomerular cells suggests the presence of S100-like calcium-binding protein-mediated activities in these cell types.