INHIBITION OF FETAL METHIONINE SYNTHASE BY NITROUS OXIDE

The activity of the enzyme methionine synthase in fetal andmaternal liver was investigated before and after exposure tonitrous oxide. Timed-pregnant rats on day 19 of gestation wereexposed to either 10% or 50% nitrous oxide for various timesup to 240 min. After exposure, fetal and maternal livers wereremoved and methionine synthase activity assayed. Normal methioninesynthase activity in the fetus was about 50% of that in themother. Both fetal and maternal methionine synthase activitydecreased progressively with increasing time of exposure tonitrous oxide and recovered only slowly after the agent wasdiscontinued.