Localization of S‐adenosylmethionine decarboxylase in murine tissues by immunohistochemistry

Abstract

S-adenosylmethionine decarboxylase (AdoMetDC), one of three key enzymes in polyamine biosynthesis, is present in minute concentrations in adult tissues, whereas increased AdoMetDC activity occurs in conjunction with differentiation and growth. The occurrence of AdoMetDC in tissues has earlier been studied by biochemical technique only. In this work, an antiserum against recombinant human AdoMetDC was used to investigate the localization of the enzyme in different mouse tissues. In all tissues studied, immunolabeling was seen in cytoplasm, while cell nuclei were negative. In the kidney, AdoMetDC immunoreactivity was confined to the inner part of the cortex; the outer part of the cortex and the medulla displayed only a weak AdoMetDC immunoreaction. In the cortex, renal tubules were strongly reactive, while renal corpuscules were weakly immunolabeled. In developing teeth, AdoMetDC immunoreactivity displayed a gradient of distribution, the immunolabeling intensity being increased from the cervical region to the tip of the cusps. In the incisor, post-secretory ameloblasts were strongly labeled. In the oral mucosa, epithelial cells demonstrated stronger immunolabeling than did cells of the subjacent connective tissue. As for muscle cells, immunoreactive material was confined to the periphery of the fibers. In vitro, treatment with DL-alpha-difluoromethylornithine (DFMO) or methylglyoxal bis-(guanylhydrazone) (MGBG) led to an increase in AdoMetDC. It can be concluded that antibodies to recombinant human AdoMetDC provide a tool for the immunohistochemical localization of AdoMetDC, and that the distribution of the enzyme in the tissues studied gives further support to the importance of polyamines in the development and functions of these organs.