RESUMO
The urinary excretion of 5-oxoproline, which may be used as an index of glycine status, was investigated in 30 normal pregnant women during different stages of pregnancy and in 18 non-pregnant female volunteers. During an 18-h study there was little variation in the 5-oxoproline/creatinine index, and a single sample gave a representative value. The excretion of 5-oxoproline/creatinine (mumol/mmol) rose progressively as pregnancy advanced (non-pregnant mean 10, SD 5, first trimester mean 46, SD 12, second trimester mean 150, SD 180, and third trimester mean 280, SD 320) and by the third trimester was over 20 times greater than in non-pregnant women. The data suggest that as pregnancy advances the endogenous production of glycine may be insufficient to satisfy the increasing demands.
Assuntos
Glicina/metabolismo , Gravidez/urina , Pirrolidinonas/urina , Ácido Pirrolidonocarboxílico/urina , Feminino , Humanos , Gravidez/metabolismo , Segundo Trimestre da Gravidez , Terceiro Trimestre da Gravidez , Fatores de TempoRESUMO
A cross-sectional study was carried out among 18 Jamaican pregnant women divided into three groups of 6 subjects according to the stage of pregnancy: group B, 12 weeks, group C, 24 weeks and group D, 33 weeks. A group (group A) of 6 non-pregnant women was selected as control. The rate of whole-body protein turnover was measured by continuous oral administration of 15N-glycine and the resting metabolic rate by the open-circuit method. All subjects had a normal pregnancy outcome. The composition of the diet on the day of the study was comparable between the four groups (approximately 80 g protein and 9.45 MJ energy) and not significantly different from the composition of the diet during the 2 d prior to the experiment. The rates of protein synthesis and breakdown were higher in groups B and C compared to group A and lower in group D where they reached values slightly higher than in group A. Estimated from urea enrichment, these rates did not vary significantly among the groups, while estimated from ammonia enrichment the difference was significant (P less than 0.05) and there was a negative correlation between the gestational age and the rate of synthesis (r = -0.63) and breakdown (r = -0.69). Nitrogen retention was comparable between the three groups of pregnant women and significantly higher than in the group A. The resting metabolic rate was similar between the groups of pregnant women. These results suggest that the rates of protein turnover observed during gestation reflect more the changes that occur in maternal than those in fetal tissues. The values for protein synthesis and nitrogen retention indicate that the amount of protein deposited during pregnancy is greater than that expected on the basis of body composition analysis. It is also suggested that as pregnancy proceeds whole-body protein turnover represents a smaller part of the resting metabolic rate.