Localization of S-adenosylhomocysteine hydrolase in the rat kidney

S-adenosylhomocysteine (SAH) hydrolase is a cytosolic enzyme present in the kidney. Enzyme activities of SAH hydrolase were measured in the kidney in isolated glomeruli and tubules. SAH hydrolase activity was 0.62 +/- 0.02 mU /mg in the kidney, 0.32 +/- 0.03 mU/mg in the glomeruli, and 0.50 +/- 0.02 mU/mg in isolated tubules. Using immunohistochemical methods, we describe t he localization of the enzyme SAH hydrolase in rat kidney with a highly spe cific antibody raised in rabbits against purified SAH hydrolase from bovine kidney. This antibody crossreacts to almost the same extent with the SAH h ydrolase from different species such as rat, pig, and human. Using light mi croscopy, SAH hydrolase was visualized by the biotin-streptavidin-alkaline phosphatase immunohistochemical procedure. SAH hydrolase immunostaining was observed in glomeruli and in the epithelium of the proximal and distal tub ules. The collecting ducts of the cortex and medulla were homogeneously sta ined. By using double immunofluorescence staining and two-channel immunoflu orescence confocal laser scanning microscopy, we differentiated the glomeru lar cells (endothelium, mesangium, podocytes) and found intensive staining of podocytes. Our results show that the enzyme SAH hydrolase is found ubiqu itously in the rat kidney. The prominent staining of SAH hydrolase in the p odocytes may reflect high rates of transmethylation.