Effect of acute and chronic epinephrine administration on clearance and metabolism of [3H]-epinephrine in trout (Oncorhynchus mykiss) |
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Authors: | A K Gamperl R G Boutilier |
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Institution: | (1) Department of Biology, Dalhousie University, B3H 4J1 Halifax, Nova Scotia, Canada;(2) Department of Zoology, University of Cambridge, Downing Street, CB2 3EJ Cambridge, UK;(3) Present address: Dept. of Biological Sciences, Simon Fraser University, V5A 1S6 Burnaby, BC, Canada |
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Abstract: | Several studies have measured the rate of catecholamine clearance, metabolism, and tissue accumulation in fish. However, no information is available on the effect of repeated stress or high circulating catecholamine levels on catecholamine clearance and metabolism. We measured the clearance and metabolism of 3H]-epinephrine (approximately 0.1 g·kg-1) in SW-acclimated rainbow trout subjected to acute (five injections in 1 day) and chronic (4 days; five injections per day) administration of 4.0 g·kg-1 epinephrine or saline. In addition, a saturation experiment, where 4.0 g·kg-1 of unlabelled epinephrine was injected concurrently with 3H]-epinephrine, investigated whether catecholamine clearance and metabolism are affected by high circulatin levels. Neither the rate constants for catecholamine clearance, nor the post-injection proportions of unmetabolised 3H]-epinephrine, deaminated 3H]-epinephrine and O-methylated 3H]-epinephrine were affected by the acute or chronic injection protocols. The concurrent injection of 3H]-epinephrine and 4.0 g·kg-1 of unlabelled epinephrine resulted in an elevated postinjection 3H:14C ratio, but increased proportions of O-methylated 3H]-epinephrine and reduced proportions of unmetabolised 3H]-epinephrine. We conclude that in fish (1) catecholamine clearance and metabolism are unlikely to be compromised by repeated exposure to acute stressors; (2) catecholamine extraction and/or metabolism is enhanced when circulating levels are high; and (3) there is a marked capacity to rapidly (minutes) clear and inactivate catecholamines that are released in response to stressful stimuli.Abbreviations CA
catecholamines
- dpm
disintegrations per minute
- MAO
monoamine oxidase
- COMT
catecholamine-O-methyltransferase
- MOPEG
3-methoxy-4-hydroxyphenylglycol
- VMA
3-methoxy-4-hydroxymendelic acid
- SW
seawater
- HPLC
high-performance liquid chromatography |
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Keywords: | Epinephrine Repeated-injections Clearance Metabolism Trout Oncorhynchus mykiss |
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