Korean J Physiol Pharmacol.
2000 Oct;4(5):417-425.
Comparison of the determinants in the differences in force-frequency
relationships between rat and rabbit left atria
- Affiliations
-
- 1Department of Pharmacology, Wonju-College of Medicine, Yonsei
University, 162 Ilsan-Dong, Wonju, Kangwon-Do, South Korea.
changmko@wonju.yonsei.ac.kr
Abstract
- 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.