title: 15N-excretion of heat-killed Lactobacillus casei in humans.
abstract: OBJECTIVE
  In the present study, Lactobacillus casei (L. casei) labelled with 15N was used to follow the metabolic fate of orally administered heat-killed 15N-labelled L. casei (15N-L.casei) in humans.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  University of Rostock, Children's Hospital, Research Laboratory.
  
  
  METHODS
  Twelve healthy adults aged 23-32 years.
  
  
  METHODS
  The subjects received 36 mg/kg body weight heat-killed 15N-L.casei and 500 mg Lactose-[13C]ureide together with breakfast. Expired air samples were taken over 14 h, whereas urine and faeces were collected over 2 days. A blood sample was taken after 2 h. 13C- and 15N-enrichments were measured by isotope ratio mass spectrometry (SerCon, UK).
  
  
  RESULTS
  The orocaecal transit time (OCTT) was reached after 4.1 h. The urinary 15N-excretion was 9.3% of the ingested dose, whereas the faecal excretion was 65.1% of the ingested dose. After 2 h, 15N-enrichment of supernatant, fibrinogen, and plasma protein precipitate amounted to 254, 11, and 2 p.p.m. excess, respectively.
  
  
  CONCLUSIONS
  In comparison to the OCTT of 4.1 h, 15N-enrichment in urinary ammonia and urinary total nitrogen already began to rise 30 min after 15N-L.casei ingestion, indicating that 15N-L.casei is rapidly digested in the small bowel. This is confirmed by 15N-enrichments of blood plasma fractions. The ingestion of heat-killed 15N-L.casei led to a total excretion of 74.4% of the ingested 15N-dose.
authors.affiliation: Children's Hospital, Research Laboratory, University of Rostock, Rostock, Germany. klaus-dieter.wutzke@med.uni-rostock.de
authors.forename: K D
authors.initials: KD
authors.lastname: Wutzke
authors.forename: V
authors.initials: V
authors.lastname: Sattinger
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001944:Breath Tests; D002247:Carbon Isotopes; D002432:Cecum / Q000382:microbiology; D004063:Digestion; D005243:Feces / Q000737:chemistry*; D005260:Female; D005772:Gastrointestinal Transit / Q000502:physiology*; D006801:Humans; D007780:Lacticaseibacillus casei; D007785:Lactose; D008297:Male; D013058:Mass Spectrometry; D009587:Nitrogen Isotopes; D019936:Probiotics; D013997:Time Factors; D014556:Urine / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D007785:Lactose