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

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2004-02, Vol.286 (2), p.398-R404
• Main Authors: Landeira-Fernandez, Ana M, Morrissette, Jeffery M, Blank, Jason M, Block, Barbara A
• Format: Article
• Language: English
• Subjects: Animals; Blotting, Western; Calcium - metabolism; Calcium-Transporting ATPases - metabolism; Electrophoresis, Polyacrylamide Gel; Heart Ventricles; Kinetics; Microsomes - enzymology; Myocardium - enzymology; Perciformes - metabolism; Sarcoplasmic Reticulum - enzymology; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Temperature; Tuna - metabolism
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00392.2003

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) Ca 2+ 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 Ca 2+ -ATPase (SERCA2) plays a major role during cardiac excitation-contraction (E-C) coupling, transporting Ca 2+ from the cytosol into the lumen of the SR and thus promoting the relaxation of the muscle. Measurements of oxalate-supported Ca 2+ uptake in SR-enriched ventricular vesicles indicated that tunas were capable of sustaining a rate of Ca 2+ uptake that was significantly higher than the mackerel. Among tunas, the cold-tolerant bluefin had the highest rates of SR Ca 2+ uptake and ATPase activity. The differences among Ca 2+ 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 Ca 2+ 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 Ca 2+ -adenosinetriphosphatase; scombrid fish; Arrhenius plot; excitation-contraction coupling Address for reprint requests and other correspondence: B. A. Block, Hopkins Marine Station, Stanford Univ., Oceanview Blvd., Pacific Grove, CA, 93950 (E-mail address: bblock{at}stanford.edu ).