Comparison of androgen regulation of ornithine decarboxylase and S-adenosylmethionine decarboxylase gene expression in rodent kidney and accessory sex organs.

Abstract

Androgen regulation of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC) activities and accumulation of the mRNAs encoding these two enzymes in rodent kidney and accessory sex organs were studied. The ODC mRNA concentration and enzyme activity were increased by androgens in kidney, prostate, and seminal vesicle of 3-day castrated mice and rats, whereas AdoMetDC mRNA and protein levels were androgen inducible only in rodent accessory sex organs. ODC and AdoMetDC mRNAs were regulated in prostate and seminal vesicles in a coordinate fashion, with the maximal levels reached within 24-48 h of steroid exposure. The extent of induction was similar for the two gene products, and ODC and AdoMetDC mRNA accumulation occurred primarily in epithelial cells of accessory sex organs, as shown by in situ hybridization studies. The murine ODC promoter contains an androgen-responsive element (ARE)-like sequence at about -910 nucleotides from the cap site; this element binds to androgen receptor in vitro, albeit with much lower affinity than some other AREs. In transient expression studies with CV-1 cells, an ODC promoter construct (pODCCAT) conferred androgen responsiveness upon the reporter gene. ODC mRNA accumulation is androgen regulated in epithelial cells of proximal tubules in both murine and rat kidney; however, different subtypes of the proximal tubular cells respond in the two species, as revealed by in situ hybridization studies. Expression of the ODC gene was induced more markedly and for a longer duration in the murine than in the rat kidney, but the initial response occurred faster in the rat kidney. The relatively slow kinetics of ODC mRNA accumulation in mouse kidney were not due to recruitment of new cells to respond; rather, in situ hybridization studies indicated that there was progressive accumulation of the mRNA in the responding cells. Collectively, these data indicate that the genes for two key enzymes in polyamine biosynthesis are not regulated in an identical fashion in different androgen target tissues, such as rodent kidney and accessory sex organs.