Immunohistochemical Demonstration of Calcium-Binding Protein Regucalcin in the Tissues of Rats: The Protein Localizes in Liver and Brain

A calcium-binding protein, regucalcin, was isolated from rat liver cytosol. Rabbit-anti-regucalcin antiserum, which was raised against regucalcin conjugated by glutaraldehyde to bovine serum albumin, was applied to glutaraldehyde-fixed whole mounts and subsequently visualized using the peroxidase-antiperoxidase methods. Rat hepatic regucalcin immunoreactivity was most pronounced in the liver and brain of rats, while it was not seen in the duodenum, testicle, spleen, lung and smooth muscle (bladder), and appeared only slightly in the kidney and heart. Control experiments using non-immune sera or adsorbed anti-rat liver regucalcin antiserum showed no staining. The present finding suggests that regucalcin localizes in the liver and brain of rats.