Properties of the omega-hydroxylation system of docosahexaenoic or arachidonic acid in brain or liver homogenate of rat.
The homogenate of a brain or liver obtained from a 1-55-day-old rat was incubated with NADPH and docosahexaenoic or arachidonic acid as the substrate. omega-Hydroxydocosahexaenoic or omega-hydroxyeicosatetraenoic acid from an incubation mixture of the homogenate was detected on a selected-ion monitoring chromatogram of reversed phase-HPLC-thermospray-mass spectrometry. omega-Hydroxylation activity in the brain homogenate considerably increased with growth up to 55 days. Activity in the liver homogenate decreased much with growth up to 55 days. omega-Hydroxylation activity in homogenates of rat brain gray matter, white matter, medula oblongata and cerebellum was much the same. omega-Hydroxylation activity of docosahexaenoic acid in rat brain homogenate was maximal at pH 7.5-8.0 in 50 mM Tris-HCl buffer and was inhibited by CO gas, metyrapone, ADP-Fe3+, heat treatment at 100 degrees C for 5 min and without NADPH. Based on these results, it is suggested that omega-hydroxylation activity is associated with cytochrome P-450 without NADPH-ADP-Fe(3+)-dependent lipid peroxidation, and the omega-hydroxylation system may be a metabolic pathway of the fatty acids in adult rat brain or neonatal rat liver. Since omega-hydroxyeicosatetraenoic acid produces relaxation of artery, it is suggested that blood flow changes in rat brain or liver with growth are caused by omega-hydroxylation activity changes in these organs with growth.
Yamane
M
M
Department of Biochemistry, Tokyo Medical College, Japan.
Abe
A
A
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D001923:Brain Chemistry / Q000502:physiology*; D002531:Cerebellum / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004281:Docosahexaenoic Acids / Q000378:metabolism*; D006900:Hydroxylation; D008099:Liver / Q000378:metabolism*; D013058:Mass Spectrometry; D008526:Medulla Oblongata / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D004281:Docosahexaenoic Acids; D016718:Arachidonic Acid