Immunohistochemical Localization of 11-Hydroxysteroid Dehydrogenase in Rat Kidney with a Monoclonal Antibody

Abstract

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.

Molecular Endocrinology of Hydroxysteroid Dehydrogenases*

“…In addition, no type I 11␤-HSD was found in several mineralocorticoid target segments in the kidney (e.g. cortical collecting ducts and collecting tubules) (85,88,89). This profile of tissue-specific expression further confirms that type I 11␤-HSD does not protect against mineralocorticoid activity of the glucocorticoids.…”

Renal medullary 11β-hydroxysteroid dehydrogenase type 1 in Dahl salt-sensitive hypertension

“…The mRNA levels of 11␤-HSD1 and 11␤-HSD2, however, were found to be similar in SS rats and Dahl salt-resistant rats (15). 11␤-HSD1 is expressed in the kidney (2,35), but the functional significance of renal 11␤-HSD1 is virtually unknown.…”

“…One possibility is that excess glucocorticoids stimulate mineralocorticoid receptors, similar to that occurs with 11␤-HSD2 deficiencies. However, 11␤-HSD1 protein seems to be localized in proximal tubules and interstitial cells (2,35), rather than the distal nephron where mineralocorticoid receptors are expressed. A recent study indicated that hexose-6-phosphate dehydrogenase, which provides the NADPH needed for the reductase activity of 11␤-HSD1, was not readily detectable in renal inner medullary interstitial cells (19).…”

Metabolism of Dexamethasone: Sites and Activity in Mammalian Tissues

“…Triamcinolone, another 9a-fluorinated corticoid, seems to be convert ed mainly into 6[5-OH-triamcinolone [25. 26], 11(5-HSD is a complex and heterogeneous enzyme system [27][28][29][30][31]. This is also indicated by the apparent cosubstrate preference of 11(5-HSD in different tissues and under different conditions.…”