title: Effects of magnesium sulphate administration on aquaporin 3 in rat gastrointestinal tract.
abstract: Aquaporin (AQP) 3 plays an important role in regulating faecal water content in the colon. We investigated the role of AQP3 in the colon in the laxative effect of magnesium sulphate (MgSO(4)), a widely used osmotic laxative. Rats were administered MgSO(4), after which faecal water content, the colon mRNA expression levels of sodium myo-inositol transporter (SMIT) and taurine transporter (TauT), the colon protein expression levels of AQP3 were examined. Faecal water content increased over time after MgSO(4) administration, and severe diarrhoea was observed between 4 and 8 h after administration. The mRNA expression levels of SMIT and TauT, which are indicators of variations in osmotic pressure, were highest at 2 h after the administration of MgSO(4) and were still elevated at 8 h after administration when compared to immediately after the administration. The immunostaining analysis showed that AQP3 is a dominant AQP in the rat colon. The protein expression levels of AQP3 in the colon increased over time following the administration of MgSO(4) and at 8 h after administration were approximately 8 times higher than baseline levels. Previously, osmotic laxatives were believed to induce diarrhoea by elevating the osmotic pressure in the intestinal tract. The results of the present study suggest that the laxative effect of MgSO(4) is not simply caused by a change in the osmotic pressure in the intestinal tract, but could be a response to increased expression of AQP3.
authors.affiliation: Department of Clinical Pharmacokinetics, School of Pharmacy and Pharmaceutical Sciences, Hoshi University, 2–4–41 Ebara, Shinagawa-ku, Tokyo 142–8501, Japan.
authors.forename: Nobutomo
authors.initials: N
authors.lastname: Ikarashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Ushiki
authors.forename: Toshihide
authors.initials: T
authors.lastname: Mochizuki
authors.forename: Takahiro
authors.initials: T
authors.lastname: Toda
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kudo
authors.forename: Kohta
authors.initials: K
authors.lastname: Baba
authors.forename: Makoto
authors.initials: M
authors.lastname: Ishii
authors.forename: Kiyomi
authors.initials: K
authors.lastname: Ito
authors.forename: Wataru
authors.initials: W
authors.lastname: Ochiai
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Sugiyama
mesh_terms: D000818:Animals; D051400:Aquaporin 3 / Q000378:metabolism*; D001692:Biological Transport; D003106:Colon / Q000187:drug effects* / Q000378:metabolism; D003967:Diarrhea / Q000209:etiology* / Q000378:metabolism; D005243:Feces / Q000737:chemistry; D007294:Inositol / Q000378:metabolism; D054368:Laxatives / Q000494:pharmacology*; D008278:Magnesium Sulfate / Q000009:adverse effects / Q000494:pharmacology*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D009995:Osmosis / Q000187:drug effects*; D009997:Osmotic Pressure; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D027981:Symporters / Q000235:genetics / Q000378:metabolism; D014867:Water / Q000378:metabolism; D000099247:Taurine Transporters
chemical_list: D051400:Aquaporin 3; D007294:Inositol; D054368:Laxatives; D008278:Magnesium Sulfate; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D012964:Sodium; D027981:Symporters; D014867:Water; D000099247:Taurine Transporters