Localization of receptors causing hypoxic bradycardia in trout (Salmo gairdneri)

1978 ◽  
Vol 56 (6) ◽  
pp. 1260-1265 ◽  
Author(s):  
Frank M. Smith ◽  
David R. Jones
Keyword(s):  
Oxygen Tension ◽  
Buccal Cavity ◽  
Cranial Nerves ◽  
Gill Arch ◽  
Cardiac Response ◽  
Salmo Gairdneri ◽  
Acclimation Temperature ◽  
Tongue Depressor ◽  
Hypoxic Water ◽  
Biological Advantage

Receptors causing the cardiac response to environmental hypoxia have been located in rainbow trout (Salmo gairdneri). Intact, unrestrained trout, acclimated to7or 16 °C. showed a marked increase in ventilation and bradycardia when exposed to hypoxia at their acclimation temperature, In experiments designed to locate the site of receptors causing hypoxic bradycardia, the buccal cavity of a fish was divided into two chambers by a tongue depressor, allowing oxygen tension of water flowing over each set of gills lo be varied independently. Irrigating one set of gills with hypoxic water [Formula: see text] while flowing hyperoxic water [Formula: see text] over the other caused heart rate to fall from 42.2 ± 0.6 (± SEM) to 26.4 ± 0.5 (± SEM) beats/min after 1 min of hypoxic water flow. Dorsal aortic [Formula: see text] was always above that recorded when both sets of gills were flushed with normoxic water [Formula: see text]. Bilateral ligation of the efferent pseudobranch artery and the pseudobranch nerve (cranial nerve IX) had no effect on the cardiac response to irrigation of one set of gills by hypoxic water. Physical removal of, or section of the nerve supply (cranial nerves IX and X) to, the first gill arch eliminated hypoxic bradycardia. The biological advantage of hypoxic bradycardia is discussed and it is suggested that gill arch receptors may function to monitor and maintain oxygen tension of blood leaving the gills.

Ambient Oxygen Tension and Transition to Anaerobic Metabolism in Three Species of Freshwater Fish

1980 ◽  
Vol 37 (8) ◽  
pp. 1216-1224 ◽  
Author(s):  
Dennis T. Burton ◽  
Alan G. Heath
Keyword(s):  
Rainbow Trout ◽  
Oxygen Tension ◽  
Anaerobic Threshold ◽  
Anaerobic Metabolism ◽  
Lepomis Macrochirus ◽  
Salmo Gairdneri ◽  
Acclimation Temperature ◽  
Brown Bullhead ◽  
Ictalurus Nebulosus ◽  
Dissociation Curves

Rainbow trout (Salmo gairdneri), bluegill (Lepomis macrochirus), and brown bullhead (Ictalurus nebulosus) were exposed to a gradual (over several hours) reduction in dissolved oxygen. Muscle and liver lactic and pyruvic acid concentrations were measured at seven environmental [Formula: see text]. The response was an increase in anaerobic metabolism of the resting fish at a threshold [Formula: see text] that varied with the species and acclimation temperature. A lower anaerobic threshold occurred after acclimation to cold in rainbow trout and possibly bluegill; cold acclimated brown bullhead did not metabolize anaerobically when held in water for 20 min with an oxygen tension near zero. The anaerobic thresholds correspond reasonably well to the relative positions of the blood oxygen dissociation curves for the three species. Only in the trout, however, does the anaerobic threshold found in this study compare to the critical oxygen tension (PC; [Formula: see text] below which aerobic metabolism becomes dependent on [Formula: see text] in the water). PC is far higher in both the bluegill and brown bullhead than the anaerobic threshold which suggests a reduction in overall energy expenditure in these species at rest when in water of low dissolved oxygen.Key words: anaerobic metabolism, lactate/pyruvate ratios, muscle, liver, rainbow trout, Salmo gairdneri; bluegill, Lepomis macrochirus; brown bullhead, Ictalurus nebulosus

scholarly journals Coronary flow in a perfused rainbow trout heart

1987 ◽  
Vol 129 (1) ◽  
pp. 107-123 ◽  
Author(s):  
A. P. Farrell
Keyword(s):  
Rainbow Trout ◽  
Coronary Flow ◽  
Coronary Circulation ◽  
Coronary Vessels ◽  
Cardiac Metabolism ◽  
Salmo Gairdneri ◽  
Acclimation Temperature ◽  
Coronary Vascular Resistance ◽  
Coronary Resistance ◽  
Temperature Dependent

A preparation was developed to perfuse the coronary circulation in working hearts from rainbow trout (Salmo gairdneri Richardson). The preparation was used to examine pressure-flow relationships for the coronary circulation as the heart generated physiological and subphysiological work loads. Coronary vascular resistance increased exponentially as coronary flow rate decreased. Coronary resistance was also influenced by cardiac metabolism and acclimation temperature. When heart rate was increased, extravascular compression increased in coronary resistance. Direct vasoconstriction of the coronary vessels, produced by injections of adrenaline into the coronary circulation, was temperature-dependent.

Trypsin from Two Strains of Rainbow Trout, Salmo gairdneri, is Influenced Differently by Assay and Acclimation Temperature

1986 ◽  
Vol 43 (8) ◽  
pp. 1664-1667 ◽  
Author(s):  
J. M. McLeese ◽  
E. Don Stevens
Keyword(s):  
Rainbow Trout ◽  
Cold Acclimation ◽  
High Strain ◽  
Specific Activity ◽  
Intestinal Morphology ◽  
Salmo Gairdneri ◽  
Acclimation Temperature ◽  
Nutrient Requirements ◽  
Lower Affinity ◽  
Pyloric Caeca

Specific activity and kinetic constants of trypsin from the pyloric caeca of two strains of rainbow trout, Salmo gairdneri, were measured using α-N-benzoyl-DL-arginine-ρ-nitroaniline∙HCl No increase in activity was observed with cold acclimation, suggesting that cold acclimation induces no increase in trypsin concentration. The apparent Km for the substrate was independent of assay temperature over the physiological range in both strains, probably to maintain high rates of catalysis at higher temperatures when nutrient requirements are high. Strain A trout produced a trypsin with lower affinity on cold acclimation, but Strain B trout did not. The two strains differed in intestinal morphology as well as in the characteristics of their trypsins.

Acylation of lysophosphatidylcholine in liver microsomes of thermally acclimated trout

1988 ◽  
Vol 255 (6) ◽  
pp. R923-R928
Author(s):  
R. C. Livermore ◽  
J. R. Hazel
Keyword(s):  
Fatty Acids ◽  
Chain Length ◽  
Liver Microsomes ◽  
Salmo Gairdneri ◽  
Acclimation Temperature ◽  
Membrane Phospholipids ◽  
Degree Of Unsaturation ◽  
Acyl Coenzyme A ◽  
Docasahexaenoic Acid ◽  
Substrate Concentrations

The specificity of acyl-coenzyme A (CoA): lysophosphatidylcholine acyltransferase (LPCAT; EC 2.3.1.23) was determined for a range for acyl-CoA substrates differing with respect to chain length and degree of unsaturation in liver microsomes of thermally acclimated (5 and 20 degrees C) rainbow trout, Salmo gairdneri. Absolute levels of oleate incorporation into phosphatidylcholine (PC) were determined at substrate concentrations in the physiological range (12 microM) and higher (64 microM). The specificity of LPCAT was determined by the extent to which competing substrates decreased the incorporation of oleate. LPCAT specificity was significantly influenced by both assay and acclimation temperature at total substrate concentrations of both 72 and 256 microM. A clear preference for 14- and 16-carbon monoenes was exhibited by LPCAT from 20 but not 5 degrees C-acclimated trout. Furthermore, LPCAT from 5 degrees C-acclimated trout preferentially incorporated long chain and polyunsaturated fatty acids (eicosadienoyl, arachidonoyl, erucoyl) and excluded 18-carbon unsaturates at an assay temperature of 5 degrees C compared with 20 degrees C; at 20 degrees C, 18-carbon unsaturates were incorporated more readily than 20-carbon species. Linolenic acid (18:3N3) was generally excluded from incorporation, reflecting a possible mechanism by which this precursor of docasahexaenoic acid (22:6N3, n - 3) remains available for modification. These results indicate that trout liver LPCAT preferentially incorporates fatty acids into PC on the basis of both chain length and degree of unsaturation in a manner consistent with the temperature-induced restructuring of membrane phospholipids.

The effect of progressive hypoxia on respiration in the dogfish (scyliorhinus canicula) at different seasonal temperatures

1975 ◽  
Vol 63 (1) ◽  
pp. 117-130 ◽  
Author(s):  
P. J. Butler ◽  
E. W. Taylor
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Oxygen Uptake ◽  
Stroke Volume ◽  
Oxygen Tension ◽  
Acclimation Temperature ◽  
Critical Oxygen Tension ◽  
Critical Oxygen ◽  
Progressive Hypoxia ◽  
Cardiac Stroke Volume

1. Dogfish were acclimated to 7, 12 or 17 degrees C and exposed to progressive hypoxia at the temperature to which they had been acclimated. During normoxia, the Q10 values for oxygen uptake, heart rate, cardiac output and respiratory frequency over the full 10 degrees C range were: 2.1, 2.1, 2.1 and 2.5 respectively. Increased acclimation temperature had no effect on cardiac stroke volume or systemic vascular resistance, although there was a decrease in branchial vascular resistance, pHa and pHv. 2. Progressive hypoxia had no effect on heart rate or oxygen uptake at 7 degrees C, whereas at 12 degrees C and 17 degrees C there was bradycardia, and a reduction in O2 uptake, with the critical oxygen tension for both variables being higher at the higher temperature. Cardiac stroke volume increased during hypoxia at each temperature, such that cardiac output did not change significantly at 12 and 17 degrees C. Neither pHa nor pHv changed significantly during hypoxia at any of the three temperatures. 3. The influence of acclimation temperatures on experimental results from poikilotherms is pointed out. Previously-published results show quantitative differences. 4. The significance of the present results with respect to the functioning and location of oxygen receptors is discussed. It is argued that as the metabolic demand and critical oxygen tension of the whole animal are increased at high acclimation temperatures the same must be the case with the oxygen receptor. This would raise the stimulation threshold and could account for the bradycardia seen during hypoxia becoming manifest at higher values of PI,O2, Pa,O2 and Pv,O2 as the acclimation temperature is raised.

Branchial receptors and cardiorespiratory reflexes in a neotropical fish, the tambaqui (Colossoma macropomum)

2000 ◽  
Vol 203 (7) ◽  
pp. 1225-1239 ◽  
Author(s):  
L. Sundin ◽  
S.G. Reid ◽  
F.T. Rantin ◽  
W.K. Milsom
Keyword(s):  
Buccal Cavity ◽  
Cranial Nerves ◽  
Breathing Frequency ◽  
Aquatic Surface Respiration ◽  
Neotropical Fish ◽  
Cardiorespiratory Control ◽  
Colossoma Macropomum ◽  
Before And After ◽  
Water Ph ◽  
Ventral Aorta

This study examined the location and physiological roles of branchial chemoreceptors involved in the cardiorespiratory responses to hypoxia and hypercarbia in a neotropical fish that exhibits aquatic surface respiration, the tambaqui (Colossoma macropomum). Fish were exposed to abrupt progressive environmental hypoxia (18. 6–1.3 kPa water P(O2)) and hypercarbia (water equilibrated with 5 % CO(2) in air, which lowered the water pH from 7.0 to 5.0). They were also subjected to injections of NaCN into the ventral aorta (to stimulate receptors monitoring the blood) and buccal cavity (to stimulate receptors monitoring the respiratory water). All tests were performed before and after selective denervation of branchial branches of cranial nerves IX and X to the gill arches. The data suggest that the O(2) receptors eliciting reflex bradycardia and increases in breathing frequency are situated on all gill arches and sense changes in both the blood and respiratory water and that the O(2) receptors triggering the elevation in systemic vascular resistance, breathing amplitude, swelling of the inferior lip and that induce aquatic surface respiration during hypoxia are extrabranchial, although branchial receptors also contribute to the latter two responses. Hypercarbia also produced bradycardia and increases in breathing frequency, as well as hypertension, and, while the data suggest that there may be receptors uniquely sensitive to changes in CO(2)/pH involved in cardiorespiratory control, this is based on quantitative rather than qualitative differences in receptor responses. These data reveal yet another novel combination for the distribution of cardiorespiratory chemoreceptors in fish from which teleologically satisfying trends have yet to emerge.

Effects of sectioning cranial nerves IX and X on the cardiac response to hypoxia in the coho salmon, Oncorhynchus kisutch

1984 ◽  
Vol 62 (5) ◽  
pp. 766-768 ◽  
Author(s):  
Frank M. Smith ◽  
Peter S. Davie
Keyword(s):  
Vagus Nerve ◽  
Surgical Procedures ◽  
Coho Salmon ◽  
Cranial Nerves ◽  
Oncorhynchus Kisutch ◽  
Glossopharyngeal Nerve ◽  
Cardiac Response

We have shown that oxygen receptors located in the first gill arches of coho salmon, and responsible for hypoxic bradycardia, may be innervated by branches of the glossopharyngeal nerve (cranial IX). Bilateral section of these branches produced a reduction in the cardiac response to rapidly induced hypoxia. Branches of the vagus nerve (cranial X) also innervate the first gill arches in salmon; when both vagal and glossopharyngeal branches to the first gill arches were sectioned, hypoxic bradycardia was reduced by the same degree as was observed when the glossopharyngeal branches alone were sectioned. The surgical procedures involved in denervation appeared to have no effect on the cardiac response to hypoxia. The pattern of innervation of oxygen receptors causing hypoxic bradycardia in salmonids is compared with the more diffuse pattern found in elasmobranchs.

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