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KMID : 0811720000040050417
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Korean Journal of Physiology & Pharmacology
2000 Volume.4 No. 5 p.417 ~ p.425
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Comparison of the Determinants in the Differences in Force- Frequency Relationships between Rat and Rabbit Left Atria
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Chang Mann Ko/Chang Mann Ko
Soon-Jin Kim
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Abstract
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The underlying mechanism commonly applicable for both the positive and negative force-frequency relationships (FFR) was pursued in left atria (LA) of rat and rabbit. The species differences in the roles of Na+/Ca2+ exchanger and sarcoplasmic reticulum (SR), which are major intracellular Ca2+ regulatory mechanisms in the heart, were examined in the amplitude accommodation to the frequency that changed from 3 Hz to the variable test frequencies for 5 minutes in the electrically field stimulated left atria (LA) of rat and rabbit. Norepinephrine strongly increased the frequency-related amplitude accommodation in both of rat and rabbit LA, while monensin, oubain or the reduced Na+ and 0 mM Ca2+ containing Tyrode solution increased the frequency-related amplitude accommodation only in the rabbit LA. Monenisn was also able to increase the frequency-related amplitude accommodation only in 1-day old rat LA but not in 4-week old rat LA that had 75% less Na+/Ca2+ exchanger with 97% higher SR than 1-day old rat LA. Taken together, it is concluded that the differences in the prevalence between myocardial Na+/Ca2+ exchanger and SR in the amplitude accommodation to the frequency-change determine the difference in the FFR between rat and rabbit heart.
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KEYWORD
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