title: Plasma retinoids after topical use of retinaldehyde on human skin.
abstract: BACKGROUND
  Retinaldehyde (RAL), a natural metabolite of beta-carotene and retinol (ROL), is tolerated by human skin after topical application.
  
  
  OBJECTIVE
  To see if topical application of a large quantity of RAL on human skin is associated with a detectable alteration of constitutive levels of plasma retinoids resulting from metabolism of RAL in the skin.
  
  
  METHODS
  Plasma retinoids [ROL, all-trans-retinoic acid (all-trans-RA), RAL, retinyl palmitate/oleate, 13-cis-RA and 4-oxo-13-cis-RA] were analyzed by high-pressure liquid chromatography. Determinations were done in 10 healthy male volunteers kept on a vitamin-A-poor diet before, during and after daily topical application of 7 mg of RAL to 40% of the body surface for 14 days.
  
  
  RESULTS
  The introduction of a restricted vitamin A diet before RAL application resulted in a decrease in the plasma levels of ROL, all-trans-RA and retinyl palmitate/oleate. Topical application of RAL did not induce an alteration of the plasma levels of retinoid metabolites. No RAL was detectable in any of the plasma samples.
  
  
  CONCLUSIONS
  The skin metabolism of topically applied RAL does not result in detectable alterations of constitutive levels of plasma retinoids in humans.
authors.affiliation: Institute for Toxicology and Embryopharmacology, Free University Berlin, Germany.
authors.forename: J O
authors.initials: JO
authors.lastname: Sass
authors.forename: E
authors.initials: E
authors.lastname: Masgrau
authors.forename: P A
authors.initials: PA
authors.lastname: Piletta
authors.forename: H
authors.initials: H
authors.lastname: Nau
authors.forename: J H
authors.initials: JH
authors.lastname: Saurat
mesh_terms: D000287:Administration, Topical; D000328:Adult; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D006801:Humans; D008297:Male; D012172:Retinaldehyde / Q000008:administration & dosage / Q000493:pharmacokinetics*; D012176:Retinoids / Q000097:blood*; D012867:Skin / Q000378:metabolism*; D012869:Skin Absorption; D014802:Vitamin A Deficiency / Q000097:blood / Q000378:metabolism
chemical_list: D012176:Retinoids; D012172:Retinaldehyde