title: Effect of nitrous oxide and methionine treatments on hepatic S-adenosylmethionine and methylation reactions in the rat.
abstract: 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.
mesh_terms: D000818:Animals; D005561:Formates / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008715:Methionine / Q000494:pharmacology*; D008745:Methylation; D009609:Nitrous Oxide / Q000494:pharmacology*; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012436:S-Adenosylmethionine / Q000378:metabolism*; D013763:Tetrahydrofolates / Q000378:metabolism
chemical_list: D005561:Formates; D010743:Phospholipids; D013763:Tetrahydrofolates; C030544:formic acid; D012436:S-Adenosylmethionine; D008715:Methionine; D009609:Nitrous Oxide; C005984:5-methyltetrahydrofolate