Testosterone Down-Regulates Ornithine Aminotransferase Gene and Up-Regulates Arginase II and Ornithine Decarboxylase Genes for Polyamines Synthesis in the Murine Kidney

Abstract

The enzymes ornithine aminotransferase (OAT) and ornithine decarboxylase (ODC) share L-ornithine as a common substrate and arginase II produces this amino acid. In the murine kidney, testosterone induced ODC gene expression and polyamine production, but it is unknown how OAT gene is expressed under androgen treatment. These experiments were designed to study the influence of testosterone on the renal expression of OAT gene. Pharmacological and physiological doses of testosterone were injected into female and castrated male mice. Total RNA and soluble proteins extracted from whole kidneys were analyzed by Northern and Western blots, respectively. The results clearly indicate that pharmacological doses of testosterone simultaneously down-regulated the level of OAT protein and up-regulated the expression of arginase II and ODC genes. Variations of the levels of OAT protein and arginase II mRNA and protein were strongly correlated with testosteronemia. Orchidectomy increased the renal level of OAT protein and decreased that of ODC and arginase II. These effects were reversed by injecting a physiological dose of testosterone into castrated male mice. In conclusion, OAT and ODC genes are inversely regulated by testosterone in the mouse kidney. Consequently, in kidneys of testosterone-treated mice, L-arginine-derived ornithine produced by arginase II might be preferentially used by ODC for putrescine production rather than by OAT. This metabolic fate of L-ornithine was facilitated by decreasing OAT gene expression. In contrast, in female and castrated male mice devoided of testosterone, OAT gene is highly expressed and L-ornithine is converted into L-glutamate.

Sexual dimorphism of ornithine decarboxylase in the mouse adrenal: influence of polyamine deprivation on catecholamine and corticoid levels

“…However, whereas in other rodent tissues such as mouse kidney (15,28) or rat prostate (39) the enzyme was stimulated by androgens, in the mouse adrenal ODC activity was downregulated by testosterone. The molecular mechanisms, by which testosterone influences ODC expression, have not been characterized in detail.…”

“…The molecular mechanisms, by which testosterone influences ODC expression, have not been characterized in detail. Although in mouse kidney (15,28), rat (39), and human prostatic cells (4, 10) the transcription of ODC gene is stimulated by testosterone, probably by the binding of AR to an androgen-responsive element-like sequence located in the ODC promoter (15), our present results indicate that the action of testosterone on adrenal ODC activity appears to be exerted at the translational level, since no differences in adrenal ODC mRNA levels between sexes were observed, whereas the amount of ODC protein responsive to ODC antibodies was higher in the adrenal cortex of female mice. The almost identical level of expression of mRNAs of several ODC-related proteins such as AZ1, AZ2, AZI, and PMF found in the adrenal gland also support the contention that sex differences in ODC expression in the adrenal of mice are related mainly to the translational control.…”

Orchidectomy Upregulates While Testosterone Treatment Downregulates the Expression of Ornithine Aminotransferase Gene in the Mouse Kidney

“…Protein transfer and equal loading of proteins were visualized on the membranes with Ponceau S solution. Blocked immunoblots were incubated with primary polyclonal rabbit antibodies raised against rat/mouse-OAT (dilution 1:1,000), rat-aldose reductase (AR; EC 1.1.1.21, dilution 1:3,000) (Lambert-Langlais et al, 2009), and monoclonal mouse β-actin (dilution 1:2,000) and glyceraldehyde-3-phosphate dehydrogenase (G3PDH; EC 1.2.1.12, dilution 1:170) antibodies, and then with a peroxidase-conjugated anti-rabbit or antimouse IgG secondary antibodies (dilution 1:10,000) as previously described (Levillain et al, 2004(Levillain et al, , 2005. Antibody binding was revealed using chemiluminescence (ECL) Western Blotting Kit.…”

“…Antibody binding was revealed using chemiluminescence (ECL) Western Blotting Kit. Details for ECL detection and quantitation of the bands have been mentioned earlier (Levillain et al, 2004(Levillain et al, , 2005.…”

“…A detailed study of the renal expression of OAT gene during the postnatal development of male and female mice revealed that puberty is the starter responsible for this sexual dimorphism (Levillain et al, 2007). In addition, the level of OAT protein has been inversely correlated with the plasma level of testosterone (Levillain et al, 2005). The present study was designed to explore the mechanismes involved in the sexual dimorphism of the expression of OAT gene in the mouse kidney.…”