Role of nitric oxide in the metabolism of arachidonic acid in the rat anterior pituitary gland.
Nitric oxide (NO) affects cyclooxygenase (COX) and lipooxygenase (LOX) activities in several tissues. The aim of this study was to investigate the effect of NO on the AA metabolism in the anterior pituitary. LOX and COX products from anterior pituitaries of Wistar male rats were determined by [14C]-AA radioconversion method. Sodium nitroprusside (NP, 0.5 mM) and DETA NONOate (1 mM), NO donors, decreased 5-hydroxy-5,8,11,14-eicosatetraenoic acid (5-HETE) synthesis (P<0.05), effects that were reversed by hemoglobin. L-arginine also inhibited LOX activity. To the contrary, the inhibition of NO synthase by L-NAME (0.5 mM) or aminoguanidine (0.5 mM) increased 5-HETE production (P<0.05). COX activity was slightly stimulated by NP and L-arginine. However, DETA NONOate induced a stimulation of the synthesis of all prostanoids (P<0.05), this effect being reversed by hemoglobin. Neither NOS inhibitors nor hemoglobin modified basal prostanoids synthesis. These results indicate that NO inhibits LOX activity and stimulates COX activity in the anterior pituitary gland. The inhibition of LOX by NO may be another mechanism involved in the effects of NO on hormone release in the anterior pituitary.
Velardez
M O
MO
Centro de Investigaciones en Reproducción, Facultad de Medicina, Universidad de Buenos Aires, 1121, Paraguay 2155, Piso 10, Buenos Aires, Argentina
Ogando
D
D
Franchi
A M
AM
Duvilanski
B H
BH
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D016166:Free Radical Scavengers / Q000494:pharmacology; D006893:Hydroxyeicosatetraenoic Acids / Q000096:biosynthesis; D008084:Lipoxygenase / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009569:Nitric Oxide / Q000494:pharmacology / Q000502:physiology*; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D016166:Free Radical Scavengers; D006893:Hydroxyeicosatetraenoic Acids; D016718:Arachidonic Acid; D009569:Nitric Oxide; C022022:5-hydroxy-6,8,11,14-eicosatetraenoic acid; D008084:Lipoxygenase; D011451:Prostaglandin-Endoperoxide Synthases