Molecular diversity of 11β-HSDs involved in a protection mechanism from the stress-mediated suppression of testosterone production

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11β-Hydroxysteroid dehydrogenase (11β-HSD) isozyme (type 1 and type 2) catalyze the interconversion of physiologically active GC and inactive forms. The presence of these isozymes was determined in neonatal pig testis and Leydig cells purified from testes by RT-PCR, Western blotting, and immunohistochemical staining. In the entire testis, a higher level of type 2 was expressed compared to type 1. Next, the direction of GC metabolism in intact Leydig cells was examined, and only oxidation from cortisol to cortisone was detected. Using a microsomal enzyme preparation from Leydig cells, type 2 exhibited potent oxidation activity, and the activity was higher than the oxidation activity catalyzed by the type 1 isozyme. Furthermore, we performed comprehensive determination of the expression of 11β-HSD isozymes mRNA by real-time RT-PCR in wide range of human tissues. The results of the present study using testis strongly suggest that not only 11β-HSD type 1 but also type 2 plays important roles in cortisol inactivation in Leydig cells of the testis, and is involved in the protection of glucocorticoid -mediated suppression of testosterone production in Leydig cells of the testis.