title: Visualization of 'water secretion' by confocal microscopy in rat salivary glands: possible distinction of para- and transcellular pathway.
abstract: Visualization of water transport in cells, tissues and organs is an important, yet still difficult, task in morphological science. By using confocal microscopy and the fluid-phase fluorescent tracer technique, we visualized water secretion and estimated the routes of water transport across the acinar epithelia in rat parotid and submandibular glands. Confocal microscopy of whole glands perfused arterially with Lucifer yellow revealed a bright fluorescence at the basolateral space of acini. Luminal space was devoid of fluorescence, but revealed it after isoproterenol pretreatment, ductal infusion of fluorescent dextrans into the lumen, or tissue dissociation by collagenase. Under these conditions, stimulation of fluid secretion with carbachol caused a rapid decline of the luminal fluorescence intensity, indicating that the secreted water washed out the fluorescent probes in the acinar lumen. In the stimulated dissociated acini, the luminal fluorescence disappeared by 15 sec, but reappeared at 30-45 sec to maintain a low plateau level. By assuming that the tight junction was 'paralyzed' by the collagenase digestion and that the paracellular fluid transport could not influence the dilution of Lucifer yellow, we estimated that the initial water secretion by CCh occurs via the transcellular pathway, while later than 30-45 sec the additional water permeates through the paracellular pathway.
authors.affiliation: Department of Anatomy, School of Medicine, Kitasato University, Sagamihara, Japan.
authors.forename: Akihisa
authors.initials: A
authors.lastname: Segawa
authors.forename: Shohei
authors.initials: S
authors.lastname: Yamashina
authors.forename: Masataka
authors.initials: M
authors.lastname: Murakami
mesh_terms: D000465:Algorithms; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D017364:Collagenases / Q000494:pharmacology; D003911:Dextrans / Q000493:pharmacokinetics; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D007545:Isoproterenol / Q000494:pharmacology; D007546:Isoquinolines / Q000493:pharmacokinetics; D008297:Male; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D010306:Parotid Gland / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D010477:Perfusion / Q000295:instrumentation / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D012235:Rhodamines / Q000493:pharmacokinetics; D012469:Salivary Glands / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D013363:Submandibular Gland / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D014867:Water / Q000378:metabolism*
chemical_list: D003911:Dextrans; D005456:Fluorescent Dyes; D007546:Isoquinolines; D012235:Rhodamines; C051311:rhodamine dextran; D014867:Water; D002217:Carbachol; C017475:lucifer yellow; D017364:Collagenases; D007545:Isoproterenol