LOCALIZATION OF D-AMINO-ACID OXIDASE MESSENGER-RNA IN THE MOUSE KIDNEY AND THE EFFECT OF TESTOSTERONE TREATMENT

D-Amino acid oxidase (DAO), which catalyzes oxidative deamination of D -amino acids, is known to be highly expressed in the kidney. This stud y was designed to examine the localization of DAO mRNA in the mouse ki dney using in situ hybridization histochemistry (ISH). For comparison, ISH for mRNA of ornithine decarboxylase (ODC), which is also highly e xpressed in the mouse kidney, was simultaneously performed. Adult, mal e mice which received 1 mg of testosterone propionate or vehicle injec tion, were sacrificed 14 h after injection and their kidneys were remo ved and processed for ISH. Hybridization signals for both mRNAs were e xclusively located over the epithelial cells of the proximal tubule in the vehicle-treated animals. Signals for the DAO mRNA were observed a t nearly the same hybridization intensity throughout the proximal tubu le, whereas hybridization signals for the ODC mRNA were observed exclu sively in the pars convoluta. Following testosterone treatment, ODC mR NA in the pars convoluta was expressed with a stronger intensity than that in the vehicle-injected animals. ODC mRNA was also expressed in t he pars recta with a weaker intensity than in the pars convoluta. On t he other hand, DAO mRNA expression was little affected by testosterone treatment. These results indicate that, although both genes are possi bly expressed in the same cells, the expression of these genes is regu lated by different mechanisms.