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: 286/2/R398    most recent 00392.2003v1 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 ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (12) Citing Articles via Google Scholar Google Scholar Articles by Landeira-Fernandez, A. M. Articles by Block, B. A. Search for Related Content PubMed PubMed Citation Articles by Landeira-Fernandez, A. M. Articles by Block, B. A.

INFLAMMATION, CYTOKINES, AND TEMPERATURE REGULATION

Temperature dependence of the Ca²⁺-ATPase (SERCA2) in the ventricles of tuna and mackerel

Tuna Research and Conservation Center, Hopkins Marine Station, Stanford University, Pacific Grove, California 93950

Submitted 16 July 2003 ; accepted in final form 28 October 2003

Recent physiological studies on the cardiovascular performance of tunas suggest that the elevated heart rates of these fish may rely on increased use of intracellular sarcoplasmic reticulum (SR) Ca²⁺ stores. In this study, we compare the cellular cardiac performance in endothermic tunas (bluefin, albacore, yellowfin) and their ectothermic sister taxa (mackerel) in response to acute temperature change. The cardiac sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA2) plays a major role during cardiac excitation-contraction (E-C) coupling, transporting Ca²⁺ from the cytosol into the lumen of the SR and thus promoting the relaxation of the muscle. Measurements of oxalate-supported Ca²⁺ uptake in SR-enriched ventricular vesicles indicated that tunas were capable of sustaining a rate of Ca²⁺ uptake that was significantly higher than the mackerel. Among tunas, the cold-tolerant bluefin had the highest rates of SR Ca²⁺ uptake and ATPase activity. The differences among Ca²⁺ uptake and ATP hydrolysis rates do not seem to result from intrinsic differences between the SERCA2 present in the different tunas, as shown by their similar temperature sensitivities and similar values for activation energy. Western blots reveal that increased SERCA2 protein content is associated with the higher Ca²⁺ uptake and ATPase activities seen in bluefin ventricles compared with albacore, yellowfin, and mackerel. We hypothesize that a key step in the evolution of high heart rate and high metabolic rate in tunas is increased activity of the SERCA2 enzyme. We also suggest that high levels of SERCA2 in bluefin tuna hearts may be important for retaining cardiac function at cold temperatures.

cardiac sarco/endoplasmic reticulum Ca²⁺-adenosinetriphosphatase; scombrid fish; Arrhenius plot; excitation-contraction coupling

This article has been cited by other articles:

				B. A. Block Physiological Ecology in the 21st Century: Advancements in Biologging Science Integr. Comp. Biol., April 1, 2005; 45(2): 305 - 320. [Abstract] [Full Text] [PDF]

				H. A. Shiels, J. M. Blank, A. P. Farrell, and B. A. Block Electrophysiological properties of the L-type Ca2+ current in cardiomyocytes from bluefin tuna and Pacific mackerel Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2004; 286(4): R659 - R668. [Abstract] [Full Text] [PDF]