Intracellular Ca2+ storage sites in the carp heart: comparison with the rat heart

Chugun, Akihito; Oyamada, Toshifumi; Temma, Kyosuke; Hara, Yukio; Kondo, Hiroshi

doi:10.1016/s1095-6433(99)00040-9

Cited by 25 publications

(14 citation statements)

References 23 publications

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“…Our findings of a higher inter-capillary distance in the ventricular spongy layer compared with the compact layer may rely on the different metabolism of the inner layer. In addition, since the development of the compact layer may relate to the swimming activity and lifestyle of the fish (Santer and Walker 1980), its volume relative to total ventricular muscle weight is higher than that in the spongy layer (Tota 1978;Breisch et al 1983;Chugun et al 1999). Our results confirm that the shorter distance between the capillaries within the outer ventricular layer increases the diffusion of metabolites maximizing the efficiency of contraction.…”

Section: Mitochondrial Organization In Bluefin Tuna Atrial and Ventrisupporting

confidence: 64%

Ultrastructure of the sarcoplasmic reticulum in cardiac myocytes from Pacific bluefin tuna

Maio

Block

2008

Cell Tissue Res

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Pacific bluefin tuna are active teleost fish with a large capacity for heat conservation and endothermy. They have a high metabolism, and hence the myocardium must be capable of sustaining elevated levels of cardiac output over a wide range of temperatures. To examine the way that the myocardial cells of bluefin tuna respond to their unique cardiac physiology, we have studied the ultrastructure of the internal membrane system and mitochondria of atrial and ventricular myocytes by light and electron microscopy. Our results reveal that cardiomyocytes of juvenile bluefin tuna posses a relatively high content of sarcoplasmic reticulum (SR), together with a large volume of mitochondria within the two (compact and spongy) ventricular compartments and in the atrial myocardium. The mitochondrial structure and distribution in bluefin tuna myocardium follow specific metabolic zonation resulting in a higher volume and lower cristae density in the compact ventricular layer than in atrium and spongy layer. The presence of junctional SR profiles and an extensive network of free SR within cells may ensure a rapid delivery of Ca(2+) to the myofibrils. This, in conjunction with transarcolemmal Ca(2+) entry, might contribute to a faster excitation-contraction-relaxation cycle and thus enhance cardiac performance, cardiac output, and the maintenance of excitability at low temperatures. We propose that the mitochondrial configuration together with the developed SR ultrastructure of bluefin tunas myocardium are important evolutionary steps for the maintenance of high heart rates and endothermy in this teleost fish.

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Section: Mitochondrial Organization In Bluefin Tuna Atrial and Ventrisupporting

confidence: 64%

Ultrastructure of the sarcoplasmic reticulum in cardiac myocytes from Pacific bluefin tuna

Maio

Block

2008

Cell Tissue Res

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“…Unlike mammals in which SR Ca 2ϩ release is prominent in EC coupling, in lower vertebrates, such as the fish, the SR is generally a poorly developed organelle of lesser importance in EC coupling (2,3,6). Depletion of SR Ca 2ϩ in zebrafish myocardium with caffeine increased diastolic Ca 2ϩ , as well as Ca 2ϩ transients.…”

Section: Discussionmentioning

confidence: 99%

Conformational changes of a Ca²⁺-binding domain of the Na⁺/Ca²⁺ exchanger monitored by FRET in transgenic zebrafish heart

Xie¹,

Ottolia²,

John³

et al. 2008

American Journal of Physiology-Cell Physiology

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cycling caused by altered NCX expression and activity has been associated with cardiac pathophysiology, including ischemia-reperfusion injury, heart failure, and arrhythmias (7,17,18).The transport activity of the exchanger is allosterically regulated by cytosolic Ca 2ϩ (25). Ca 2ϩ binds to two Ca 2ϩ -binding domains (CBD1 and CBD2) located in the large intracellular loop and activates the exchanger (1, 4, 9, 10, 13). The function of CBD1 has been analyzed in most detail. Mutations of acidic residues (e.g., D447V or D498I) within CBD1 decrease Ca 2ϩ affinity (11 Here, we present the use of the zebrafish Danio rerio as an expression system for studying the Ca 2ϩ regulation of the cardiac NCX in vivo. We generated transgenic zebrafish with cardiac-specific expression of the CBD1 linked to yellow (YFP) and cyan fluorescent protein (CFP). Using FRET, we monitored conformational changes of the Ca 2ϩ regulatory domain of NCX during EC coupling in the myocardium of intact zebrafish. With this transgenic fish model, we demonstrate that the increase in Ca 2ϩ transients of intact hearts induced by the positive inotropic agents ouabain and isoproterenol leads to an increase in the state of activation of CBD1 and, therefore, most likely of the intact NCX. METHODSZebrafish maintenance and generation of transgenic lines. Zebrafish were maintained under standard conditions (26). The AB strain was used as the wild-type line. To generate transgenic zebrafish expressing canine YFP-CBD1-CFP, the YFP-CBD1-CFP DNA (15), excised with NheI/NotI, was subcloned into the T2K ␣kss MCS vector (a kind gift of Dr. K Kawakami) (8) downstream of the cardiac myosin light-chain promoter to create the T2K YFP-CBD1-CFP construct. Transposase mRNA was synthesized in vitro from pCS-TP using the mMESSAGE mMACHINE SP6 kit. The T2K YFP-CBD1-CFP plasmid and transposase mRNA were mixed at final concentrations of 25 ng/l in RNase-free water. Approximately 1 nl of a DNA/RNA solution was microinjected into zebrafish embryos at the one-cell stage by microinjection. Injected embryos were examined for YFP expression under a Zeiss SV-11 epifluorescence microscope at 2 days postfertilization (dpf), and only embryos with YFP expression were raised to adulthood. F0 founder fish were identified by crossing with wild-type zebrafish and examining YFP expression of 2-day-old F1 embryos. A similar strategy was utilized to obtain transgenic zebrafish expressing a YFP-CBD1-CFP mutant (D447V/D498I).

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“…Ca 2ϩ release from the cardiac SR is triggered by Ca 2ϩ binding to the cytosolic site of the RyR, which induces opening of the Ca 2ϩ release channel (17). In fish hearts, Ca 2ϩ binding affinity of RyRs on the cytosolic side is often much lower than in mammalian hearts (11,56), which may stabilize SR Ca 2ϩ and thereby enable much higher SR Ca 2ϩ loads. Consistent with this, SS and Max Ca 2ϩ loads of the SR in the three fish species correlate negatively with Ca 2ϩ sensitivity of their RyRs to cytosolic Ca 2ϩ .…”

Section: Discussionmentioning

confidence: 99%

“…A major functional characteristic of the fish cardiac SR is the massive Ca 2ϩ loading capacity of the SR, which is likely an outcome of low Ca 2ϩ sensitivity of the release mechanism (11,56) and high stability of SR Ca 2ϩ stores. Sensitivity and stability are antagonistic properties of a system; hence, the high sensitivity of the Ca 2ϩ release system of endothermic hearts has probably evolved from the low sensitivity of a Ca 2ϩ release system of ectothermic animals with the trade-off being low stability of SR Ca 2ϩ stores.…”

Section: Perspectives and Significancementioning

confidence: 99%

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

Haverinen

Vornanen

2009

American Journal of Physiology-Regulatory, Integrative and Comp

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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) Ca(2+) content, was tested by comparing steady-state (SS) and maximal (Max) Ca(2+) 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 degrees C (cold-acclimation, CA) or 18 degrees C (warm-acclimation, WA), and SR Ca(2+) content was released by a rapid application of 10 mM caffeine to single cardiac myocytes; its amount was determined from the Na(+)-Ca(2+) exchange current at 18 degrees C. SS Ca(2+) load was larger in atrial (304-915 micromol/l) than ventricular (224-540 micromol/l) myocytes in all fish species (P < 0.05), and the same was true for Max SR Ca(2+) content: 550-1,522 micromol/l and 438-840 micromol/l for atrial and ventricular myocytes, respectively (P < 0.05). Consistent with the hypothesis, acclimation to cold increased Ca(2+) load of the cardiac SR in the burbot heart, but contrary to the hypothesis, temperature acclimation did not affect SR Ca(2+) content in rainbow trout and crucian carp hearts. Furthermore, there was an inverse relation between SR Ca(2+) content and Ry sensitivity of contraction force: the species with the smallest SR Ca(2+) content (burbot) is most sensitive to Ry. Collectively, these findings show that SR Ca(2+) content of fish cardiac myocytes is several times larger than that in mammalian cardiac SR.

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Intracellular Ca2+ storage sites in the carp heart: comparison with the rat heart

Cited by 25 publications

References 23 publications

Ultrastructure of the sarcoplasmic reticulum in cardiac myocytes from Pacific bluefin tuna

Ultrastructure of the sarcoplasmic reticulum in cardiac myocytes from Pacific bluefin tuna

Conformational changes of a Ca²⁺-binding domain of the Na⁺/Ca²⁺ exchanger monitored by FRET in transgenic zebrafish heart

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

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Intracellular Ca2+ storage sites in the carp heart: comparison with the rat heart

Cited by 25 publications

References 23 publications

Ultrastructure of the sarcoplasmic reticulum in cardiac myocytes from Pacific bluefin tuna

Ultrastructure of the sarcoplasmic reticulum in cardiac myocytes from Pacific bluefin tuna

Conformational changes of a Ca2+-binding domain of the Na+/Ca2+ exchanger monitored by FRET in transgenic zebrafish heart

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

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Conformational changes of a Ca²⁺-binding domain of the Na⁺/Ca²⁺ exchanger monitored by FRET in transgenic zebrafish heart