title: Ultraviolet B irradiation of the mouse eye induces pigmentation of the skin more strongly than does stress loading, by increasing the levels of prohormone convertase 2 and α-melanocyte-stimulating hormone.
abstract: BACKGROUND
  In previous studies, we made the unexpected finding that in mice, ultraviolet (UV)B irradiation of the eye increased the concentration of α-melanocyte-stimulating hormone (α-MSH) in plasma, and systemically stimulated epidermal melanocytes.
  
  
  OBJECTIVE
  To compare the extent of the pigmentation induced by social and restraint stress (which activate the hippocampus-pituitary system) with that induced by UVB irradiation.
  
  
  METHODS
  DBA/2 and sham-operated or hypophysectomized DBA/2 mice were subjected to local UVB exposure using a sunlamp directed at the eye, and two types of stress (social and restraint) were imposed.
  
  
  RESULTS
  UVB irradiation of the eye or exposure to stress loading both increased the number of Dopa-positive melanocytes in the epidermis, and hypophysectomy strongly inhibited the UVB-induced and stress-induced stimulation of melanocytes. Irradiation of the eye caused a much greater increase in dopamine than did the stress load. Both UVB eye irradiation and stress increased the blood levels of α-MSH and adrenocorticotropic hormone (ACTH). In addition, the increase in plasma α-MSH was greater in animals subjected to UVB eye irradiation than in those subjected to stress loading, whereas the reverse occurred for plasma ACTH. UVB irradiation to the eye and stress loading increased the expression of prohormone convertase (PC)1/3 and PC2 in the pituitary gland. The increase in expression of pituitary PC2 was greater in animals subjected to UVB eye irradiation than to stress, whereas no difference was seen between the two groups for the increase in PC1/3.
  
  
  CONCLUSIONS
  UVB eye irradiation exerts a stronger effect on pigmentation than stress loading, and is related to increased levels of α-MSH and PC2.
authors.affiliation: Department of Dermatology, Osaka City University Graduate School of Medicine, Japan. hiramoto@msic.med.osaka-cu.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Hiramoto
authors.forename: Y
authors.initials: Y
authors.lastname: Yamate
authors.forename: H
authors.initials: H
authors.lastname: Kobayashi
authors.forename: M
authors.initials: M
authors.lastname: Ishii
authors.forename: E F
authors.initials: EF
authors.lastname: Sato
authors.forename: M
authors.initials: M
authors.lastname: Inoue
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000378:metabolism / Q000528:radiation effects; D000818:Animals; D004817:Epidermis / Q000502:physiology / Q000528:radiation effects; D005123:Eye / Q000528:radiation effects*; D007016:Hypophysectomy; D008544:Melanocytes / Q000528:radiation effects; D051379:Mice; D008811:Mice, Inbred DBA; D010902:Pituitary Gland / Q000378:metabolism; D045706:Proprotein Convertase 2 / Q000378:metabolism / Q000528:radiation effects*; D012880:Skin Pigmentation / Q000502:physiology / Q000528:radiation effects*; D013312:Stress, Physiological / Q000502:physiology*; D014466:Ultraviolet Rays; D000521:alpha-MSH / Q000378:metabolism / Q000528:radiation effects*
chemical_list: D000521:alpha-MSH; D000324:Adrenocorticotropic Hormone; D045706:Proprotein Convertase 2