title: Rh protein expression in branchial neuroepithelial cells, and the role of ammonia in ventilatory control in fish.
abstract: Bill Milsom has made seminal contributions to our understanding of ventilatory control in a wide range of vertebrates. Teleosts are particularly interesting, because they produce a 3rd, potentially toxic respiratory gas (ammonia) in large amounts. Fish are well known to hyperventilate under high environmental ammonia (HEA), but only recently has the potential role of ammonia in normal ventilatory control been investigated. It is now clear that ammonia can act directly as a ventilatory stimulant in trout, independent of its effects on acid-base balance. Even in ureotelic dogfish sharks, acute elevations in ammonia cause increases in ventilation. Peripherally, the detection of elevated ammonia resides in gill arches I and II in trout, and in vitro, neuroepithelial cells (NECs) from these arches are sensitive to ammonia, responding with elevations in intracellular Ca(2+) ([Ca(2+)]i). Centrally, hyperventilatory responses to ammonia correlate more closely with concentrations of ammonia in the brain than in plasma or CSF. After chronic HEA exposure, ventilatory responsiveness to ammonia is lost, associated with both an attenuation of the [Ca(2+)]i response in NECs, and the absence of elevation in brain ammonia concentration. Chronic exposure to HEA also causes increases in the mRNA expression of several Rh proteins (ammonia-conductive channels) in both brain and gills. "Single cell" PCR techniques have been used to isolate the individual responses of NECs versus other gill cell types. We suggest several circumstances (post-feeding, post-exercise) where the role of ammonia as a ventilatory stimulant may have adaptive benefits for O2 uptake in fish.
authors.affiliation: Dept. of Biology, McMaster University, Hamilton, Canada; Key Laboratory of Marine Bio-resources Sustainable Utilization, South China Sea Institute of Oceanology, Guangzhou, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Dept. of Biology, McMaster University, Hamilton, Canada; Dept. of Physiology, University of Arizona, Tucson, USA; Bamfield Marine Sciences Centre, Bamfield, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Michele Nawata
authors.affiliation: Bamfield Marine Sciences Centre, Bamfield, Canada; SPHERE, Dept. of Biology, University of Antwerp, Antwerp, Belgium.
authors.forename: Gudrun
authors.initials: G
authors.lastname: De Boeck
authors.affiliation: Dept. of Biology, McMaster University, Hamilton, Canada; Bamfield Marine Sciences Centre, Bamfield, Canada; Dept. of Zoology, University of British Columbia, Vancouver, Canada. Electronic address: woodcm@zoology.ubc.ca.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
mesh_terms: D000641:Ammonia / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001934:Branchial Region / Q000166:cytology / Q000502:physiology; D005260:Female; D029941:Fish Proteins / Q000235:genetics / Q000502:physiology*; D005880:Gills / Q000166:cytology / Q000502:physiology; D008297:Male; D046569:Neuroepithelial Cells / Q000502:physiology*; D017686:Oncorhynchus mykiss / Q000235:genetics / Q000502:physiology*; D010100:Oxygen / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012143:Respiratory Physiological Phenomena / Q000187:drug effects
chemical_list: D029941:Fish Proteins; D012333:RNA, Messenger; D000641:Ammonia; D010100:Oxygen
keywords: 1st gill arch; Ammonia; Brain; Chemoreceptors; Elasmobranchs; Neuroepithelial cells; Rhesus glycoproteins; Serotonin; Teleost fish; Ventilation