title: Whole body protein turnover can be measured non-invasively in women using the end product method with [15N]glycine to show changes with the menstrual cycle and pregnancy.
abstract: OBJECTIVE
  To assess the effect of the menstrual cycle and pregnancy on whole body protein turnover.
  
  
  METHODS
  Whole body protein turnover was determined using oral [15N]glycine in normal women from enrichment measured in urine at days 7 and 14 of the menstrual cycle and in pregnant women at 17-20 weeks and 30-32 weeks gestation.
  
  
  RESULTS
  Nitrogen flux was 38.2 (5.8) mg N/kg/h using a single dose and 31.1+/-4.1 mg N/kg/h with prime-intermittent doses-the same as in men using the same methods. Nitrogen flux around the time of ovulation, 32.3 (8.2) mg N/kg/h, was greater than at day 7, 26.8 (3.0) mg N/kg/h (P<0.05). For women taking the contraceptive pill flux at day 7, 22.7 (0.2) mg N/kg/h, and day 14, 21.3 (2.1) mg N/kg/h, were similar, but were lower at day 14 than for women not taking the pill (P<0.05). Protein synthesis increased between mid and late pregnancy (1.7-2.0 g N/h; P=0.012), but not when expressed in relation to body weight
  
  
  CONCLUSIONS
  Protein turnover can be measured reproducibly in women using a non-invasive method, provided care is taken to standardize the conditions, and especially the duration over which urine is collected. There is an increase around the time of ovulation when hormonal levels are at their highest and during pregnancy the results obtained are similar to those reported using [13C]leucine.
  
  
  BACKGROUND
  University of Southampton and Medical Research Council.
authors.affiliation: Institute of Human Nutrition, University of Southampton, Southampton, UK. iohn@soton.ac.uk
authors.forename: A A
authors.initials: AA
authors.lastname: Jackson
authors.forename: S L
authors.initials: SL
authors.lastname: Duggleby
authors.forename: G
authors.initials: G
authors.lastname: Grove
mesh_terms: D000284:Administration, Oral; D000328:Adult; D015992:Body Mass Index; D005260:Female; D005998:Glycine / Q000008:administration & dosage / Q000652:urine*; D006801:Humans; D008297:Male; D008598:Menstruation / Q000378:metabolism*; D010060:Ovulation / Q000378:metabolism; D011247:Pregnancy / Q000378:metabolism*; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism*
chemical_list: D011506:Proteins; D005998:Glycine