Localization of arachidonate 12-lipoxygenase in parenchymal cells of porcine anterior pituitary.
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.
Department of Biochemistry, School of Medicine, Tokushima University, Japan.
N
N
Ueda
A
A
Hiroshima
K
K
Natsui
F
F
Shinjo
T
T
Yoshimoto
S
S
Yamamoto
K
K
Ii
K
K
Gerozissis
F
F
Dray
D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000378:metabolism*; D001091:Arachidonate Lipoxygenases / Q000378:metabolism*; D001095:Arachidonic Acids / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D008970:Molecular Weight; D009928:Organ Specificity; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000201:enzymology* / Q000648:ultrastructure; D013552:Swine
D001095:Arachidonic Acids; D001091:Arachidonate Lipoxygenases; D001092:Arachidonate 12-Lipoxygenase