title: The influence of hydration status during prolonged endurance exercise on salivary antimicrobial proteins.
abstract: OBJECTIVE
  Antimicrobial proteins (AMPs) in saliva including secretory immunoglobulin A (SIgA), lactoferrin (SLac) and lysozyme (SLys) are important in host defence against oral and respiratory infections. This study investigated the effects of hydration status on saliva AMP responses to endurance exercise.
  
  
  METHODS
  Using a randomized design, 10 healthy male participants (age 23 ± 4 years, [Formula: see text] 56.8 ± 6.5 ml/kg/min) completed 2 h cycling at 60 % [Formula: see text] in states of euhydration (EH) or dehydration (DH) induced by 24 h fluid restriction. Unstimulated saliva samples were collected before, during, immediately post-exercise and each hour for 3 h recovery.
  
  
  RESULTS
  Fluid restriction resulted in a 1.5 ± 0.5 % loss of body mass from baseline and a 4.3 ± 0.7 % loss immediately post-exercise. Pre-exercise urine osmolality was higher in DH than EH and overall, saliva flow rate was reduced in DH compared with EH (p < 0.05). Baseline SIgA secretion rates were not different between conditions; however, exercise induced a significant increase in SIgA concentration in DH (161 ± 134 to 309 ± 271 mg/L) which remained elevated throughout 3 h recovery. SLac secretion rates increased from pre- to post-exercise in both conditions which remained elevated in DH only. Overall, SLac concentrations were higher in DH than EH. Pre-exercise SLys concentrations were lower in DH compared with EH (1.6 ± 2.0 vs. 5.5 ± 6.7 mg/L). Post-exercise SLys concentrations remained elevated in DH but returned to pre-exercise levels by 1 h post-exercise in EH.
  
  
  CONCLUSIONS
  Exercise in DH caused a reduction in saliva flow rate yet induced greater secretion rates of SLac and higher concentrations of SIgA and SLys. Thus, DH does not impair saliva AMP responses to endurance exercise.
authors.affiliation: School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK, Sophie.Killer@outlook.com.
authors.forename: Sophie C
authors.initials: SC
authors.lastname: Killer
authors.forename: Ida S
authors.initials: IS
authors.lastname: Svendsen
authors.forename: Michael
authors.initials: M
authors.lastname: Gleeson
mesh_terms: D001642:Bicycling; D003681:Dehydration / Q000276:immunology*; D015444:Exercise; D006801:Humans; D008297:Male; D010807:Physical Endurance / Q000276:immunology*; D012463:Saliva / Q000276:immunology*; D012469:Salivary Glands / Q000276:immunology*; D012471:Salivary Proteins and Peptides / Q000276:immunology*; D055815:Young Adult
chemical_list: D012471:Salivary Proteins and Peptides