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An in vivo respirometer–metabolism chamber was used to obtain respiratory–cardiovascular physiology under normoxic and hypoxic conditions, and xenobiotic gill absorption (flux) data on adult lake trout ( Salvelinus namaycush ) over a 48-h exposure period at 11±1°C. An oral membrane was used to separate inspired and expired water flows, providing the first direct measurements of chemical flux across the gills of lake trout. Overall mean values (±S.D.) for normoxic respiratory function were: ventilation rate (V R )=53±9 # min −1 , ventilation volume (Q V )=7±2 l kg −1 h −1 , respiratory stroke volume (SV R )=2±1 ml, oxygen consumption (VO 2 )=39±8 mg kg −1 h −1 , oxygen utilization (U)=53±14%, and effective respiratory volume (Q W )=4±1 l kg −1 h −1 . The resting Q V , Q W , and VO 2 seen in these lake trout were lower than seen previously in other salmonids. No significant differences ( P ≥0.05) in respiratory function were detected between males and females. Trout subjected to hypoxia (30% of saturation) showed no changes in U or VO 2 , while V R decreased (42±6 # min −1 ), Q V increased (22±6 l kg −1 h −1 ) and SV R increased (8±3 ml). Cardiovascular and blood gas measurements determined under normoxic conditions were heart rate (H R )=73±8 # min −1 , cardiac output (Q C )=15±2 ml kg −1 min −1 , cardiac stroke volume (SV H )=0.2 ml kg −1 min −1 , dorsal aortic blood pressure (D BP )=34±1 mm Hg, ventral aortic blood pressure (V BP )=45±1 mm Hg, and venous oxygen partial pressure (P V O 2 )=26±2 mm Hg. Initial 1-h mean±S.D. chemical gill extraction efficiencies (EE) for tetrachloroethane (TCE), pentachloroethane (PCE), and hexachloroethane (HCE) were 42±8, 58±16, and 68±17%, respectively. Forty-eight hour EE of 9±1% for TCE (log K OW =2.39) and 21±4% for PCE (log K OW =3.06) indicated they were approaching steady-state, in contrast to 54±13% for HCE (log K OW =4.04) which was not near steady-state. The EE for all three chloroethanes were significantly ( P X ) values for waterborne TCE, PCE, and HCE were 64±11, 120±14, and 226±29 l kg −1 , respectively. Lake trout Cl X and Q W for TCE, PCE, and HCE demonstrated an approximate 1:1 relationship indicative of water-flow limited gill absorption. Chemical gill absorption observed for the lake trout and chloroethanes was similar to the rainbow trout ( Oncorhynchus mykiss ) from previous investigations and provided further support for the water-flow limited model of chemical flux across fish gills for mid-hydrophobic chemicals (log K OW =3.0–6.0). |
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