Immunohistochemical localization of 11-hydroxysteroid dehydrogenase in rat kidney with monoclonal antibody

Monoclonal antibody (MAb) against 11-hydroxysteroid dehydrogenase (11-HSD) has been raised by immunization of female balb/c mice. 11-HSD from solubilized rat renal microsomal protein could be bound in a modified ELISA using antimouse IgG and MAb against 11-HSD. On Western blots of solubilized rat renal microsomes the MAb recognized a single protein band of an approximate molecular weight of 35 kD. Immunohistochemical staining of rat renal tissue with the above MAb and the APAAP staining technique displayed a heterogenous reginal and subcellular distribution: glomeruli and arterioles were practically devoid of specific staining, as were epithelial cells in inner and outer medulla. Intense immunostaining was observed in PCT and particularly in PST, appearing granular with highest density around the nuclei. Here the enzyme bound to intracellular membranes may exert an autocrine function such as signal inactivation. In contrast to cortex, staining of interstitial cells was observed in renal medulla. The latter localization is compatible with the concept of a paracrine function of 11-HSD which might prevent corticosterone from gaining access to collecting duct cells.