title: Transepidermal water loss in developing rats: role of aquaporins in the immature skin.
abstract: In the extremely preterm infant, high transepidermal water loss (TEWL) can result in severe dehydration. TEWL has been attributed to the structural properties of the epidermis but might also be influenced by mechanisms that facilitate water transport. To investigate whether aquaporins (AQP) may be involved in the extreme losses of water through immature skin, we examined the presence and cellular distributions of AQP-1 and AQP-3 in embryonic and adult rat skin by immunohistochemistry. The expression of AQP mRNA in skin was analyzed with the use of semiquantitative reverse transcription-PCR. In rat pups of different embryonic (E) and postnatal (P) ages (days), TEWL and skin hydration were measured. AQP-1 was detected in dermal capillaries, and AQP-3 was abundant in basal epidermal layers. Both AQP displayed several times higher expression in embryonic than in adult skin. TEWL was highest at embryonic day 18 (E18) (133 +/- 18 g/m2h) and lower at E20 (25 +/- 1 g/m2h) and P4 (9 +/- 2 g/m2h). Skin hydration measured as skin electrical capacitance paralleled TEWL, being highest in fetal skin (794 +/- 15 pF at E18) and decreasing to 109 +/- 11 pF at E20 and to 0 +/- 0 pF at P4. We conclude that, as in infants, water loss through the skin of rats decreases markedly with maturation during the perinatal period. The expression and cellular localization of the AQP are such that they might influence skin hydration and water transport and contribute to the high losses of water through the immature skin.
authors.affiliation: Department of Women's and Children's Health, Uppsala University Children's Hospital, Sweden. johan.agren@kbh.uu.se
authors.forename: Johan
authors.initials: J
authors.lastname: Agren
authors.forename: Sergey
authors.initials: S
authors.lastname: Zelenin
authors.forename: Mattias
authors.initials: M
authors.lastname: Håkansson
authors.forename: Ann-Christine
authors.initials: AC
authors.lastname: Eklöf
authors.forename: Anita
authors.initials: A
authors.lastname: Aperia
authors.forename: Lene N
authors.initials: LN
authors.lastname: Nejsum
authors.forename: Soren
authors.initials: S
authors.lastname: Nielsen
authors.forename: Gunnar
authors.initials: G
authors.lastname: Sedin
mesh_terms: D000367:Age Factors; D000818:Animals; D051398:Aquaporin 1; D051400:Aquaporin 3; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D025802:Electric Capacitance; D004817:Epidermis / Q000196:embryology* / Q000254:growth & development / Q000378:metabolism*; D005260:Female; D005333:Fetus / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D014867:Water / Q000378:metabolism; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: C496022:Aqp1 protein, rat; C496029:Aqp3 protein, rat; D020346:Aquaporins; D012333:RNA, Messenger; D014867:Water; D051398:Aquaporin 1; D051400:Aquaporin 3