title: Elevated serum concentrations of beta-glucuronide metabolites and 4-oxoretinol in lactating sows after treatment with vitamin A: a model for evaluating supplementation in lactating women.
abstract: BACKGROUND
  The effects of large doses of preformed vitamin A, such as those provided in supplementation programs for the prevention of deficiency, on total serum vitamin A have been inadequately investigated.
  
  
  OBJECTIVE
  This study characterized the time course of serum vitamin A metabolites in lactating sows after single high doses of retinyl ester.
  
  
  METHODS
  Lactating sows were fitted with jugular catheters and subsequently fed either 1.05 or 2.1 mmol retinyl ester (n = 6/group) or a corn oil vehicle (n = 3). Blood was collected at baseline and at intervals to 48 h and analyzed by gradient HPLC for retinol, retinyl esters, and metabolites.
  
  
  RESULTS
  The mean (+/-SD) total serum vitamin A concentration peaked at 1 h (3.69 +/- 4.0 mumol/L) and 2 h (7.70 +/- 6.8 mumol/L) in the low- and high-dose groups, respectively (P < 0.05). Retinyl esters accounted for most of the serum vitamin A in both groups at peak time points. Mean serum retinol concentrations changed little and accounted for most of the serum vitamin A at baseline (94% and 97% for the low- and high-dose groups, respectively) but for only 22% and 14% at peak times for the low- and high-dose groups, respectively. Postdosage increases were observed for total vitamin A and retinyl esters, 4-oxoretinol, retinoyl beta-glucuronide, and retinyl beta-glucuronide but not for retinoic acid.
  
  
  CONCLUSIONS
  Serum retinol concentration remains relatively static after a large dose of preformed vitamin A and therefore is not an appropriate measure of intervention efficacy. The increases in beta-glucuronide metabolites and 4-oxoretinol suggest a preventive role against a rise in retinoic acid and retinol.
authors.affiliation: Interdepartmental Graduate Program in Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Kristina L
authors.initials: KL
authors.lastname: Penniston
authors.forename: Sherry A
authors.initials: SA
authors.lastname: Tanumihardjo
mesh_terms: D000818:Animals; D004224:Diterpenes; D005260:Female; D020719:Glucuronides / Q000097:blood*; D007774:Lactation / Q000187:drug effects / Q000378:metabolism*; D000084562:Retinyl Esters; D013552:Swine; D014801:Vitamin A / Q000031:analogs & derivatives* / Q000097:blood* / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D004224:Diterpenes; D020719:Glucuronides; D000084562:Retinyl Esters; D014801:Vitamin A; C009166:retinol acetate; C041819:4-oxoretinol