title: Biological effect of far-infrared therapy on increasing skin microcirculation in rats.
abstract: OBJECTIVE
  Insufficient microcirculation of skin leads to acute and chronic tissue ischemia in cases of trauma, reconstructive surgery, diabetes mellitus and peripheral arterial occlusive disease. The autonomic nervous system and nitric oxide (NO) play important roles in maintaining blood perfusion of the skin. Far-infrared (FIR) therapy provides low energy of light emitted from an artificial radiator and has been used to treat many vascular-related disorders. Nevertheless, the mechanisms through which FIR works remain unclear. The present study aims to test the hypothesis that the effect of FIR is through increasing skin microcirculation by a mechanism other than its thermal effect.
  
  
  METHODS
  Sixty rats were used in the present study. A WS TY301 FIR emitter was placed 20 cm above the rats. Skin temperature and blood flow were continuously measured by a K-type thermocouple. Under laboratory control, the abdominal skin temperature steadily increased from 38-39 degrees C, and was kept at constant temperature. Skin microcirculation was measured with a continuous laser Doppler flowmeter.
  
  
  RESULTS
  There was no significant change of skin blood flow during FIR treatment. Skin blood flow increased significantly soon after the removal of the FIR emitter. The stimulating effect on skin blood flow was more significant in the rats treated with FIR for 45 min and could be sustained as long as 60 min. These findings suggested a non-thermic biological effect of FIR on skin microcirculation. The promotive effect of FIR on increasing skin blood flow was not influenced by pretreatment of APP (atropine, propranolol and phentolamine), but was suppressed by pretreatment with NG-nitro-L-arginine methyl ester (an endothelial nitric oxide synthase inhibitor).
  
  
  CONCLUSIONS
  In conclusion, FIR therapy exerts a NO-related biological effect to increase skin microcirculation in rats. This might bring into perspective the clinical application of FIR to treat ischemic disease by augmenting L-arginine/NO pathway.
authors.affiliation: Institute of Molecular and Cellular Biology, Department of Life Science, National Tsing-Hua University, Hsinchu, and Division of General Surgery, Department of Surgery, Veterans General Hospital, Taipei, Taiwan.
authors.forename: Shi-Yau
authors.initials: SY
authors.lastname: Yu
authors.forename: Jen-Hwey
authors.initials: JH
authors.lastname: Chiu
authors.forename: Shiaw-Der
authors.initials: SD
authors.lastname: Yang
authors.forename: Yu-Chen
authors.initials: YC
authors.lastname: Hsu
authors.forename: Wing-Yiu
authors.initials: WY
authors.lastname: Lui
authors.forename: Chew-Wun
authors.initials: CW
authors.lastname: Wu
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D007259:Infrared Rays / Q000627:therapeutic use*; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000528:radiation effects*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000098:blood supply* / Q000187:drug effects; D012881:Skin Temperature
chemical_list: D001285:Atropine; D011433:Propranolol; D019331:NG-Nitroarginine Methyl Ester; D010646:Phentolamine