[Investigations into methionine metabolism in normal and disturbed gestation on the basis of animal experiments]

One hundred and fifty Han Wistar rats, divided into three groups, non-pregnant controls, pregnant animals and pregnant animals with disturbed gestation, were each given an injection of 10 muCi 75-Se-methionine, administered into a tail vein--in the case of the two pregnant groups on the 20th day of gestation. The disturbance of gestation in the third group had been caused by ligating the uterine vessels on the 17th day of gestation. This resulted in a reduction in the number of live fetuses and a significant growth retardation in surviving fetuses which had lain close to the site of the ligature. Ten animals of each group were killed 30, 60, 180, 360 and 1440 minutes after the methionine injection and the activity in the blood, liver and fetoplacental unit was measured. From the measured activity (divided by the specimen weight and multiplied by the total weight of the animal divided by the activity of the injected dose) the relative organ activity was calculated; its duration may be regarded as a measurement of the nature and extent of methionine metabolism. It was found that the increase in amino-acid metabolism (especially in the liver) which takes place in pregnancy is less pronounced in cases of disturbed gestation. In the fetoplacental unit a high level of transmethylation activity was found. When gestation is disturbed, transmethylation is also increased, while in contrast a reduced rate of protein synthesis was observed. The division of the unit into fetus and placenta shows that the high transmethylation activity only takes place in the fetus, corresponding to the enzyme pattern in the fetus and placenta. The redistribution of fetal methionine utilization in favor of transmethylation where gestation is disturbed is systemically controlled. Simultaneously there is a localized, circulation-dependent, absolute reduction in diaplacental transport.