HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 297/4/R1180    most recent 00022.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Haverinen, J. Articles by Vornanen, M. PubMed PubMed Citation Articles by Haverinen, J. Articles by Vornanen, M.

Articles

Comparison of sarcoplasmic reticulum calcium content in atrial and ventricular myocytes of three fish species

University of Joensuu, Faculty of Biosciences, Joensuu, Finland

Submitted March 3, 2009 ; accepted in final form August 13, 2009

Ryanodine (Ry) sensitivity of cardiac contraction differs between teleost species, between atrium and ventricle, and according to the thermal history of the fish. The hypothesis that variability in Ry sensitivity of contraction is due to species-specific, chamber-specific, and temperature-related differences in the sarcoplasmic reticulum (SR) Ca²⁺ content, was tested by comparing steady-state (SS) and maximal (Max) Ca²⁺ loads of the SR in three teleost fish, rainbow trout (Oncorhynchus mykiss), burbot (Lota lota), and crucian carp (Carassius carassius), which differ in the extent of SR contribution to excitation-contraction coupling. Fish were acclimated at 4°C (cold-acclimation, CA) or 18°C (warm-acclimation, WA), and SR Ca²⁺ content was released by a rapid application of 10 mM caffeine to single cardiac myocytes; its amount was determined from the Na⁺-Ca²⁺ exchange current at 18°C. SS Ca²⁺ load was larger in atrial (304–915 µmol/l) than ventricular (224–540 µmol/l) myocytes in all fish species (P < 0.05), and the same was true for Max SR Ca²⁺ content: 550–1,522 µmol/l and 438–840 µmol/l for atrial and ventricular myocytes, respectively (P < 0.05). Consistent with the hypothesis, acclimation to cold increased Ca²⁺ load of the cardiac SR in the burbot heart, but contrary to the hypothesis, temperature acclimation did not affect SR Ca²⁺ content in rainbow trout and crucian carp hearts. Furthermore, there was an inverse relation between SR Ca²⁺ content and Ry sensitivity of contraction force: the species with the smallest SR Ca²⁺ content (burbot) is most sensitive to Ry. Collectively, these findings show that SR Ca²⁺ content of fish cardiac myocytes is several times larger than that in mammalian cardiac SR.

excitation-contraction coupling; sarcoplasmic reticulum calcium load; caffeine; sodium-calcium exchange current