Plasticity of excitation-contraction coupling in fish cardiac myocytes.
Ultrastructure, molecular composition and electrophysiological properties of cardiac myocytes and functional characteristics of the fish heart suggest that cycling of extracellular Ca(2+) is generally more important than intracellular cycling of Ca(2+) stores of the sarcoplasmic reticulum (SR) in activating contraction of fish cardiac myocytes. This is especially true for the ventricle. However, prominent species-specific differences exist in cardiac excitation-contraction coupling and in the relative roles of extracellular and intracellular Ca(2+) sources among the teleostean fish. In fact, in some fish species (tunas, burbot) the SR of atrial myocytes, under certain circumstances, may act as the major source of systolic Ca(2+). These interspecific differences are obviously an outcome of evolutionary adaptation to different habitats and modes of activity in these habitats. There is also substantial intraspecific variation in the SR Ca(2+)-release-to-SL-Ca(2+) influx ratio depending on acute and chronic temperature changes. Consequently excitation-contraction coupling of the fish cardiac myocytes is not a fixed entity, but rather a highly variable and malleable process that enables fish to have an appropriate cardiac scope to exploit a diverse range of environments.
Vornanen
Matti
M
Department of Biology, University of Joensuu, P.O. Box 111, Finland. matti.vornanen@joensuu.fi
Shiels
Holly A
HA
Farrell
Anthony P
AP
D000064:Acclimatization / Q000502:physiology; D000200:Action Potentials; D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling; D005399:Fishes / Q000502:physiology*; D006329:Heart Conduction System / Q000502:physiology; D008955:Models, Cardiovascular; D009200:Myocardial Contraction / Q000502:physiology*; D011188:Potassium / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
D020746:Calcium Channels, L-Type; D011188:Potassium