title: Aquaporin 1: examination of its expression and localization in normal human skeletal muscle tissue.
abstract: To examine aquaporin 1 (AQP1) expression in skeletal muscle tissue precisely, we performed reverse transcription-polymerase chain reaction (RT-PCR) at RNA level and immunoblot analysis, immunohistochemistry and immunoelectron microscopy at protein level. The RT-PCR study of total RNA from normal human skeletal muscle showed a strong single band of AQP1. At the protein level we used two commercially available antibodies, both of which recognize the cytoplasmic domain of the AQP1 molecule. One antibody gave positive results. Immunoblot of muscle extract showed a 30-kDa band protein, the molecular weight of which corresponded to that of AQP1. Immunohistochemically, AQP1 was immunostained at the myofiber surface both in type 1 and type 2 myofibers with almost the same intensity, and its staining pattern was rather diffuse and irregular compared with that of the anti-dystrophin antibody. The endomysial endothelial cells were also immunolabeled. Immunoelectron microscopy revealed that the immunogold particles indicating the presence of the AQP1 molecule were present along the inside surface of the muscle plasma membrane. However, another antibody showed negative results except for the endomysial endothelial cells which were positively stained. We drew the conclusion that AQP1 is expressed at the endomysial capillary endothelial cell and further AQP1 may be expressed at the human skeletal myofiber plasma membrane.
authors.affiliation: Department of Neurology, Showa University Fujigaoka Hospital, Yokohama, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Jimi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Wakayama
authors.forename: Masahiko
authors.initials: M
authors.lastname: Inoue
authors.forename: Hiroko
authors.initials: H
authors.lastname: Kojima
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Oniki
authors.forename: Yoko
authors.initials: Y
authors.lastname: Matsuzaki
authors.forename: Seiji
authors.initials: S
authors.lastname: Shibuya
authors.forename: Hajime
authors.initials: H
authors.lastname: Hara
authors.forename: Joji
authors.initials: J
authors.lastname: Takahashi
mesh_terms: D000906:Antibodies; D051398:Aquaporin 1 / Q000235:genetics*; D002462:Cell Membrane / Q000648:ultrastructure; D004730:Endothelium, Vascular / Q000166:cytology; D005786:Gene Expression Regulation; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D007231:Infant, Newborn; D016253:Microscopy, Immunoelectron; D018482:Muscle, Skeletal / Q000166:cytology* / Q000473:pathology / Q000502:physiology* / Q000648:ultrastructure; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000906:Antibodies; D051398:Aquaporin 1; D012313:RNA