title: The duration of enzyme induction in orocaecal transit time measurements.
abstract: OBJECTIVE
  In this study, the duration of enzyme induction provoked by unlabelled lactose ureide (LU) in orocaecal transit time (OCTT) measurements with lactose-[(13)C]ureide ((13)C-LU) was evaluated.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  University of Rostock, Children's Hospital, Research Laboratory.
  
  
  METHODS
  Fifteen healthy adults aged 19-54 years.
  
  
  METHODS
  One-half gram of (13)C-LU was administered together with a continental breakfast. After 1 week, the test was repeated after pre-dosing of 5 x 100 mg LU on the day before the study began. The (13)C-LU ingestion was repeated under identical conditions but without pre-dosing 1 and 3 weeks after pre-dosing. Expired air samples were taken over 14 h. (13)CO(2)-enrichment was measured by isotope ratio mass spectrometry (SerCon, Crewe, UK). The OCTT was calculated from the interval between (13)C-LU administration and the detection of a significant and sustained (13)C-rise of 2 delta over baseline in breath.
  
  
  RESULTS
  Without pre-dosing, an OCTT of 419+/-82 min was measured. The pre-dosing resulted in higher (13)C-enrichments and caused a significant OCTT shortening of 311+/-99 min (P=0.028). One and 3 weeks after pre-dosing, the measured OCTT again increased to 404+/-124 and 379+/-103 min, respectively.
  
  
  CONCLUSIONS
  Pre-dosing with LU before pulse labelling with (13)C-LU led to an induction of enzyme activity and resulted in a definitive estimation of the OCTT when using a threshold of 2 delta over baseline. After 1 and 3 weeks, respectively, the OCTT was no longer significantly different to those without pre-dosing, indicating the disappearance of enzyme induction. Therefore, a pre-dosing with LU on the day before (13)C-LU ingestion is essential for OCTT measurements.
authors.affiliation: 1Research Laboratory Gastroenterology and Nutrition, Children's Hospital, University of Rostock, Rostock, Germany. klaus-dieter.wutzke@med.uni-rostock.de
authors.forename: K D
authors.initials: KD
authors.lastname: Wutzke
authors.forename: M
authors.initials: M
authors.lastname: Schütt
mesh_terms: D000328:Adult; D019540:Area Under Curve; D001944:Breath Tests / Q000379:methods*; D002245:Carbon Dioxide / Q000032:analysis; D002247:Carbon Isotopes; D018592:Cross-Over Studies; D004790:Enzyme Induction; D005260:Female; D005772:Gastrointestinal Transit / Q000502:physiology*; D006801:Humans; D007785:Lactose; D008297:Male; D013058:Mass Spectrometry; D008875:Middle Aged; D013997:Time Factors; D014508:Urea / Q000031:analogs & derivatives*
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide; C121442:lactose ureide; D014508:Urea; D007785:Lactose