MOUSE 17-BETA-HYDROXYSTEROID DEHYDROGENASE TYPE-2 MESSENGER-RNA IS PREDOMINANTLY EXPRESSED IN HEPATOCYTES AND IN SURFACE EPITHELIAL-CELLS OF THE GASTROINTESTINAL AND URINARY TRACTS

17 beta-Hydroxysteroid dehydrogenase (17HSD) type 2 efficiently cataly zes the conversion of the high activity 17 beta-hydroxy forms of sex s teroids into less potent 17-ketosteroids. In the present study in situ hybridization was utilized to analyze the cellular localization of 17 HSD type 2 expression in adult male and female mice. The data indicate that 17HSD type 2 mRNA is expressed in several epithelial cell layers , including both absorptive and secretory epithelia as well as protect ive epithelium. In both males and females, strong expression of 17HSD type 2 was particularly detected in epithelial cells of the gastrointe stinal and urinary tracts. The mRNA was expressed in the stratified sq uamous epithelium of the esophagus, and surface epithelial cells of th e stomach, small intestine and colon. The hepatocytes of the liver and the thick limbs of the loops of Henle in the kidneys, as well as the epithelium of the urinary bladder, also showed strong expression of 17 HSD type 2 mRNA in both male and female mice. In the genital tracts, l ow 17HSD type 2 expression was detected in the seminiferous tubules, t he uterine epithelial cells and the surface epithelium of the ovary. E xpression of the mRNA was also detected in the sebaceous glands of the skin. The results indicate that in both male and female mice, 17HSD t ype 2 is expressed mainly in the various epithelial cell types of the gastrointestinal and urinary tracts, and therefore suggest a role for the enzyme in steroid inactivation in a range of tissues and cell type s not considered as classical sex steroid target tissues.