Localization of arachidonate 12-lipoxygenase in parenchymal cells of porcine anterior pituitary

• Published in: The Journal of biological chemistry 1990-02, Vol.265 (4), p.2311-2316
• Main Authors: UEDA, N, HIROSHIMA, A, NATSUI, K, SHINJO, F, YOSHIMOTO, T, YAMAMOTO, S, II, K, GEROZISSIS, K, DRAY, F
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Arachidonate 12-Lipoxygenase - metabolism; Arachidonate Lipoxygenases - metabolism; Arachidonic Acids - isolation & purification; Biological and medical sciences; Chromatography, High Pressure Liquid; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Immunoenzyme Techniques; Immunohistochemistry; Microscopy, Electron; Molecular Weight; Organ Specificity; Oxidoreductases; Pituitary Gland, Anterior - cytology; Pituitary Gland, Anterior - enzymology; Pituitary Gland, Anterior - ultrastructure; Swine
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)39977-6

12-Lipoxygenases oxygenate arachidonic acid producing its 12S-hydroperoxy derivative and are well known as platelet and leukocyte enzymes. When a peroxidase-linked immunoassay of the enzyme according to the avidin-biotin method was applied to the cytosol fractions from various parts of porcine brain, a considerable amount of the enzyme was found in the anterior pituitary. The enzyme level (about 200 ng/mg cytosol protein) corresponded to about 6% of the enzyme content in porcine peripheral leukocytes. Posterior and intermediate lobes showed about one-tenth of the enzyme level of anterior pituitary. Other parts of porcine brain contained the 12-lipoxygenase in amounts below 7 ng/mg cytosol protein. The cytosol fraction (0.7 mg of protein) of anterior pituitary produced 12S-hydroxy-5,8,10,14-eicosatetraenoic acid from 25 microM arachidonic acid in about 34% conversion at 24 degrees C for 5 min, giving a specific enzyme activity about 3 nmol/min/mg protein. Furthermore, various octadecapolyenoic acids were oxygenated almost as fast as the arachidonate 12-oxygenation. When anterior pituitary was investigated immunohistochemically with anti-12-lipoxygenase antibody, most of the immunostained cells were certain parenchymal cells with granules, which were not blood cells. These biochemical and immunohistochemical results provide a good reason for considering that 12-lipoxygenase does play an important role in pituitary function.