Nitric Oxide Production by Primary Liver Cells Isolated from Amino Acid Diet–Fed Rats

Abstract

Primary mixed liver cells were isolated from rats that had been fed an amino acid (AA) diet in which natural protein was replaced with a defined mixture of pure AAs. Nitric oxide (NO) production from these cells in vitro was monitored using a nitric oxide (NO)-selective fluorescent probe, diaminofluorescein, followed by flow cytometric analysis. High levels of NO fluorescence were seen in approximately half of liver cells isolated from rats fed an AA diet for 1-7 days, whereas there was baseline fluorescence in cells obtained from regular diet-fed rats. The apparent size of NO-producing cells was smaller than those not producing NO. The production of NO was inhibited when rats were treated with either inducible NO synthase (iNOS)- or endothelial NOS-specific inhibitor, and an inhibitor for iNOS induction during AA diet feeding. L-arginine or L-glutamine (material for L-arginine biosynthesis) enriched diet showed the same NO augmentation as in AA diet. It is speculated that a high content of free L-arginine in AA diet may have caused enhanced NO production.