Involvement of Ca2+ waves in excitation-contraction coupling of rat atrial cardiomyocytes
2001; Elsevier BV; Volume: 70; Issue: 6 Linguagem: Inglês
10.1016/s0024-3205(01)01436-9
ISSN1879-0631
AutoresHikaru Tanaka, Haruko Masumiya, Toshiyuki Sekine, Junya Kase, Toru Kawanishi, Takao Hayakawa, Setsuya Miyata, Yoichi Sato, Ryu Nakamura, Koki Shigenobu,
Tópico(s)Ion channel regulation and function
ResumoTwo-dimensional and line-scan analyses of the early phase Ca2+ transients in rat cardiomyocytes were performed with a rapid-scanning laser confocal microscope and fluo-3 to elucidate the mechanism of activation of Ca2+ release from the sarcoplasmic reticulum in atrial myocytes which lack a well developed T-tubular network. On electrical stimulation of ventricular myocytes, Ca2+ concentration began to rise earliest at the Z-line level and became uniform throughout the cytoplasm within about 10 msec. In contrast, on stimulation of atrial myocytes, the earliest rise in Ca2+ occurred at the cell periphery and then spread to the cell interior; cytoplasmic Ca2+ became uniform after more than 30msec. The velocity of the propagation of rise in Ca2+ was 112 +/- 5.1 microm/sec (n = 10), which was similar to that of spontaneous Ca2+ waves observed in atrial and ventricular myocytes. No difference in frequency, amplitude and kinetics of spontaneous Ca2+ sparks was observed between the subsarcolemmal and central regions of atrial myocytes. Ryanodine concentration-dependently decreased the contractile force of isolated rat atrial and ventricular tissue preparations; the sensitivity was higher in atrial myocytes. The present study visualized the involvement of a propagated Ca2+-induced-Ca+ release mechanism in atrial but not ventricular myocytes. This difference may underlie some of the atrioventricular difference in response to physiological and pharmacological stimuli.
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