Document Detail

Temperature acclimation modifies sinoatrial pacemaker mechanism of the rainbow trout heart.
MedLine Citation:
PMID:  17008459     Owner:  NLM     Status:  MEDLINE    
The hypothesis of pacemaker level origin of thermal compensation in heart rate was tested by recording action potentials (AP) in intact sinoatrial tissue and enzymatically isolated pacemaker cells of rainbow trout acclimated at 4 degrees C (cold) and 18 degrees C (warm). With electrophysiological recordings, the primary pacemaker was located at the base of the sinoatrial valve, where a morphologically distinct ring of tissue comprising myocytes and neural elements was found by histological examination. Intrinsic beating rate of this pacemaker was higher in cold-acclimated (46 +/- 6 APs/min) than warm-acclimated trout (38 +/- 3 APs/min; P < 0.05), and a similar difference was seen in beating rate of isolated pacemaker cells (44 +/- 6 vs. 38 +/- 6 APs/min; P < 0.05), supporting the hypothesis that thermal acclimation modifies the intrinsic pacemaker mechanism of fish heart. Inhibition of sarcoplasmic reticulum (SR) with 10 microM ryanodine and 1 microM thapsigargin did not affect heart rate in either warm- or cold-acclimated trout at 11 degrees C but reduced heart rate in warm-acclimated trout from 74 +/- 2 to 42 +/- 6 APs/min (P < 0.05) at 18 degrees C. At 11 degrees C, a half-maximal blockade of the delayed rectifier K+ current (I(Kr)) with 0.1 microM E-4031 reduced heart rate more in warm-acclimated (from 45 +/- 1 to 24 +/- 5 APs/min) than cold-acclimated trout (56 +/- 3 vs. 48 +/- 2 APs/min), whereas I(Kr) density was higher and AP duration less in cold-acclimated trout (P > 0.05). Collectively, these findings suggest that a cold-induced increase in AP discharge frequency is at least partly due to higher density of the I(Kr) in the cold-acclimated trout, whereas contribution of SR Ca2+ release to thermal compensation of heart rate is negligible.
Jaakko Haverinen; Matti Vornanen
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-09-28
Journal Detail:
Title:  American journal of physiology. Regulatory, integrative and comparative physiology     Volume:  292     ISSN:  0363-6119     ISO Abbreviation:  Am. J. Physiol. Regul. Integr. Comp. Physiol.     Publication Date:  2007 Feb 
Date Detail:
Created Date:  2007-02-02     Completed Date:  2007-03-08     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901230     Medline TA:  Am J Physiol Regul Integr Comp Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  R1023-32     Citation Subset:  IM    
Department of Biology, University of Joensuu, PO Box 111, 80101 Joensuu, Finland.
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MeSH Terms
Acclimatization / physiology*
Action Potentials / physiology
Biological Clocks / physiology*
Calcium Channels / drug effects,  metabolism
Cell Size
Delayed Rectifier Potassium Channels / drug effects,  metabolism
Heart / physiology*
Muscle Cells / drug effects,  metabolism
Oncorhynchus mykiss / physiology*
Patch-Clamp Techniques
Piperidines / pharmacology
Potassium Channel Blockers / pharmacology
Potassium Channels / metabolism
Pyridines / pharmacology
Ryanodine / pharmacology
Sarcoplasmic Reticulum / drug effects,  metabolism
Sinoatrial Node / cytology,  physiology*
Thapsigargin / pharmacology
Reg. No./Substance:
0/Calcium Channels; 0/Delayed Rectifier Potassium Channels; 0/Piperidines; 0/Potassium Channel Blockers; 0/Potassium Channels; 0/Pyridines; 113558-89-7/E 4031; 15662-33-6/Ryanodine; 67526-95-8/Thapsigargin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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