Developmental Differences in Production of Lipoxygenase Metabolites by Ovine Lungs

Abstract

This study determined age-related differences in production of lipoxygenase metabolites by ovine lungs. Lungs of near-term fetal (146 ± 2 days gestation), neonatal (8 ± 2 days), and adult sheep were homogenized and 9000g fraction (9000g) cytosol, and microsomes were prepared by differential centrifugation. These subcellular fractions were incubated for 10 min at 37°C, either alone, with [¹⁴C]arachidonic acid ([¹⁴C]AA), or with A23187. Hydroxyeico-satetraenok acids (HETEs) and leukotrienes (LTs) were extracted from incubation media and quantitated by HPLC. All three lung subcellular fractions metabolized [¹⁴C]AA into 5-, 12-, and 15-HETEs. Production of each HETE was greater in neonatal and adult 9000g and microsomes than in fetal microsomes. Leukotriene production from [¹⁴C]AA by 9000g, cytosol, and microsomes was greater, the older the animal. Production of LTs by microsomes was greater than that by cytosol at all ages. LT production from endogenous AA increased significantly on stimulation with 5 μM A23187, and was inhibited by 50 μM NDGA. In each case, LTC₄ was metabolized to LTD₄ and LTE₄. The data show that ovine lungs metabolize exogenous and endogenous AA into 5-, 12-, and 15-HETEs and LTs and that production of lipoxygenase metabolites by the lung increases with age. Also, in the ovine lung, 5-lipoxygenase is more membrane bound than cytosolic.

Key Words:

• leukotrienes
• eicosanoids
• cytosol
• hydroxyeicosatetraenoic acids
• glutathione