title: Immunolocalization of aquaporin-1 in the mechanoreceptive Ruffini endings in the periodontal ligament.
abstract: Previous ultrastructural studies have suggested an axon-Schwann cell interaction in the periodontal Ruffini ending, a primary mechanoreceptor. However, no information is available on the transport mechanism between them. The present study examined the immunolocalization of aquaporin-1 (AQP1) and -4 (AQP4), a member of the water-selective channel, in the periodontal Ruffini endings of the rat incisors and trigeminal ganglion. In addition, the expression of mRNA for AQP1 and 4 was detected in the trigeminal ganglion by a RT-PCR technique. A single PCR product of the sizes anticipated for AQP1 and 4 was detectable in a reverse transcripted cDNA sample from the trigeminal ganglion, whose neurons innervate the periodontal Ruffini endings. An AQP1 immunoreaction was recognizable in the axon terminals of the periodontal Ruffini endings as well as their associated terminal Schwann cells, as confirmed with a double staining with AQP1 and either PGP9.5 or S-100 protein. However, no immunoreaction for AQP4 was found in periodontal Ruffini endings. Although the AQP4 immunoreaction was localized in some satellite cells - but never in neurons - of the trigeminal ganglion, 16.1% trigeminal neurons showed the AQP1 immunoreaction. Furthermore, the AQP1 immunoreaction was found in certain satellite cells which surrounded AQP1-positive or -negative neurons. An analysis of a cross-sectional area of these positive neurons demonstrated that approximately 66.9% of the positive neurons were 400-1000 microm2 (671.4+/-172.4 microm2), indicating that they could be categorized as medium-sized neurons which mediate mechanotransduction. These findings suggest that AQP1 controls water transport in the periodontal Ruffini endings.
authors.affiliation: Division of Oral Anatomy, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Chuo-ku, Niigata 951-8514, Japan.
authors.forename: Batheegama Gammacharige Tharanga Lakmali
authors.initials: BG
authors.lastname: Nandasena
authors.forename: Akiko
authors.initials: A
authors.lastname: Suzuki
authors.forename: Megumi
authors.initials: M
authors.lastname: Aita
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Kawano
authors.forename: Kayoko
authors.initials: K
authors.lastname: Nozawa-Inoue
authors.forename: Takeyasu
authors.initials: T
authors.lastname: Maeda
mesh_terms: D000818:Animals; D051398:Aquaporin 1 / Q000235:genetics / Q000378:metabolism*; D051401:Aquaporin 4 / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D048429:Cell Size; D007150:Immunohistochemistry; D007180:Incisor / Q000294:innervation; D008297:Male; D008465:Mechanoreceptors / Q000166:cytology / Q000378:metabolism*; D040542:Mechanotransduction, Cellular / Q000502:physiology; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism*; D010513:Periodontal Ligament / Q000294:innervation*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D009418:S100 Proteins / Q000378:metabolism; D027161:Satellite Cells, Perineuronal / Q000166:cytology / Q000378:metabolism; D012668:Trigeminal Ganglion / Q000166:cytology / Q000378:metabolism*; D043222:Ubiquitin Thiolesterase / Q000378:metabolism; D014882:Water-Electrolyte Balance / Q000502:physiology
chemical_list: C496022:Aqp1 protein, rat; C496032:Aqp4 protein, rat; D051401:Aquaporin 4; D012333:RNA, Messenger; D009418:S100 Proteins; D051398:Aquaporin 1; C489034:UCHL1 protein, rat; D043222:Ubiquitin Thiolesterase