title: Thymidine and methionine syntheses in pregnant rats exposed to nitrous oxide.
abstract: The dose-dependent effects of nitrous oxide on thymidine and methionine syntheses were investigated in pregnant rats. Female Sprague-Dawley rats were exposed on day 9 of gestation to 0.75%, 7.5%, or 75% nitrous oxide for 24 h. Immediately and 72 h after exposure, a deoxyuridine-suppression test was performed on maternal bone marrow and a methionine synthetase assay was performed on maternal liver to assess thymidine and methionine syntheses, respectively. Inhibition of thymidine synthesis was seen after exposure to 7.5% and 75%, but not after 0.75%, nitrous oxide. Recovery was complete 72 h after exposure. Methionine synthetase activity was abolished at all concentrations of nitrous oxide tested and did not return to control values 72 h after exposure. Fetal weight and gross appearance were not affected by exposure to nitrous oxide; however, the observed decrease in thymidine and methionine syntheses after nitrous oxide exposure may account for its teratogenic effects.
mesh_terms: D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000378:metabolism; D000818:Animals; D003857:Deoxyuridine; D005260:Female; D008715:Methionine / Q000096:biosynthesis*; D009609:Nitrous Oxide / Q000494:pharmacology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D013936:Thymidine / Q000096:biosynthesis*
chemical_list: D008715:Methionine; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D009609:Nitrous Oxide; D013936:Thymidine; D003857:Deoxyuridine