Molecular characterization of bovine placental and ovarian 20 alpha-hydroxysteroid dehydrogenase

Abstract

The enzyme 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD) catalyzes the conversion of progesterone to its inactive form, 20 alpha-hydroxyprogesterone. This enzyme plays a critical role in the regulation of luteal function in female mammals. In this study, we conducted the characterization and functional analyses of bovine 20 alpha-HSD from placental and ovarian tissues. The nucleotide sequence of bovine 20 alpha-HSD showed significant homology to that of goats (96%), humans (84%), rabbits (83%), and mice (81%). The mRNA levels increased gradually throughout the estrous cycle, the highest being in the corpus luteum (CL) 1 stage. Northern blot analysis revealed a 1.2 kb mRNA in the bovine placental and ovarian tissues. An antibody specific to bovine 20 alpha-HSD was generated in a rabbit immunized with the purified, recombinant protein. Recombinant 20 alpha-HSD protein produced in mammalian cells had a molecular weight of similar to 37 kDa. Bacterially expressed bovine 20 alpha-HSD protein showed enzymatic activity. The expression pattern of the 20 alpha-HSD protein in the pre-parturition placenta and the CL1 stage of the estrous cycle was similar to the level of 20 alpha-HSD mRNA expression. Immunohistochemical analysis also revealed that bovine 20 alpha-HSD protein was intensively localized in the large luteal cells during the late estrous cycle. Reproduction (2011) 142 723-731