title: Does ammonia trigger hyperventilation in the elasmobranch, Squalus acanthias suckleyi?
abstract: We examined the ventilatory response of the spiny dogfish, to elevated internal or environmental ammonia. Sharks were injected via arterial catheters with ammonia solutions or their Na salt equivalents sufficient to increase plasma total ammonia concentration [TAmm]a by 3-5 fold from 145±21μM to 447±150μM using NH4HCO3 and a maximum of 766±100μM using (NH4)2SO4. (NH4)2SO4 caused a small increase in ventilation frequency (+14%) and a large increase in amplitude (+69%), while Na2SO4 did not. However, CO2 partial pressure (PaCO2) also increased and arterial pHa and plasma bicarbonate concentration ([HCO3(-)]a) decreased. NH4HCO3 caused a smaller increase in plasma ammonia resulting in a smaller but significant, short lived increases in ventilation frequency (+6%) and amplitude (36%), together with a rise in PaCO2 and [HCO3(-)]a. Injection with NaHCO3 which increased pHa and [HCO3(-)]a did not change ventilation. Plasma ammonia concentration correlated significantly with ventilation amplitude, while ventilation frequency showed a (negative) correlation with pHa. Exposure to high environmental ammonia (1500μM NH4HCO3) did not induce changes in ventilation until plasma [TAmm]a increased and ventilation amplitude (but not frequency) increased in parallel. We conclude that internal ammonia stimulates ventilation in spiny dogfish, especially amplitude or stroke volume, while environmental ammonia only stimulates ventilation after ammonia diffuses into the bloodstream.
authors.affiliation: Bamfield Marine Sciences Centre, 100 Pachena Rd, Bamfield, British Columbia V0R 1B0, Canada; SPHERE, Department of Biology, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium. Electronic address: gudrun.deboeck@uantwerpen.be.
authors.forename: Gudrun
authors.initials: G
authors.lastname: De Boeck
authors.affiliation: Bamfield Marine Sciences Centre, 100 Pachena Rd, Bamfield, British Columbia V0R 1B0, Canada; Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada; Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, USA; Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
mesh_terms: D000641:Ammonia / Q000097:blood / Q000633:toxicity*; D000818:Animals; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood; D004284:Dogfish / Q000097:blood / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D006985:Hyperventilation / Q000139:chemically induced*; D008297:Male; D010100:Oxygen / Q000097:blood; D012119:Respiration / Q000187:drug effects*; D013223:Statistics as Topic; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D000641:Ammonia; D010100:Oxygen
keywords: Ammonia; Dogfish; Respiration; Respiratory gas; Shark; Ventilation