Immunohistochemical localization of guinea-pig leukotriene B-4 12-hydroxydehydrogenase/15-ketoprostagland in 13-reductase

We have cloned cDNA for leukotriene B-4 12-hydroxydehydrogenase (LTB4 12-HD )/15-ketoprostaglandin 13-reductase (PGR) from guinea-pig liver. LTB4 12-HD catalyzes the conversion of LTB4 into 12-keto-LTB4 in the presence of NADP (+), and plays an important role in inactivating LTB4. The cDNA contained a n ORF of 987 by that encodes a protein of 329 amino-acid residues with a 78 % identity with porcine LTB4 12-HD. The amino acids in the putative NAD(+)/ NADP(+) binding domain are well conserved among the pig, guinea-pig, human, rat, and rabbit enzymes. The guinea-pig LTB4 12-HD (gpLTB(4) 12-HD) was ex pressed as a glutathione S-transferase (GST) fusion protein in Escherichia coli, which exhibited similar enzyme activities to porcine LTB4 12-HD. We e xamined the 15-ketoprostaglandin 13-reductase (PGR) activity of recombinant gpLTB(4) 12-HD, and confirmed that the K-cat of the PGR activity is higher than that of LTB4 12-HD activity by 200-fold. Northern and Western blot an alyses revealed that gpLTB(4) 12-HD/PGR is widely expressed in guinea-pig t issues such as liver, kidney, small intestine, spleen, and stomach. We carr ied out immunohistochemical analyses of this enzyme in various guinea-pig t issues. Epithelial cells of calyx and collecting tubules in kidney, epithel ial cells of airway, alveoli, epithelial cells in small intestine and stoma ch, and hepatocytes were found to express the enzyme. These findings will l ead to the identification of the unrevealed roles of PGs and LTs in these t issues.