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AB Makar and TR Tephly
Nitrous oxide administration to experimental animals leads to significant alterations in the hepatic folate pathway. This pathway is closely linked to the metabolism of methionine and S-adenosylmethionine (AdoMet), two compounds that play a central role in biologically important methylation reactions. This study was carried out to assess whether nitrous oxide administration to animals can affect the metabolism of AdoMet and the AdoMet-dependent methylation reactions. Exposure of rats to a mixture of nitrous oxide and oxygen (50:50) for 2 hr reduced hepatic AdoMet levels. However, when methionine was administered to these rats, hepatic AdoMet rapidly increased to levels that were significantly higher than those observed in air-exposed animals. Concomitant with this increase, there was a significant and marked increase in the rate of methylation of phospholipids and carboxymethylation of proteins. Thus, nitrous oxide, in addition to its inhibitory effect on 5-methyltetrahydrofolate:homocysteine methyltransferase (methionine synthase, EC 2.1.1.13) activity, possesses another effect. It increases the rate of conversion of exogenously administered methionine into AdoMet with a subsequent increase in the rate of methylation of key cellular constituents.
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D. W. Horne Neither Methionine nor Nitrous Oxide Inactivation of Methionine Synthase Affect the Concentration of 5,10-Methylenetetrahydrofolate in Rat Liver J. Nutr., February 1, 2003; 133(2): 476 - 478. [Abstract] [Full Text] [PDF] |
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