Jun-Hei Chang1, Pao-Yun Cheng2, Chih-Hsueng Hsu3, Yao-Chang Chen4, Po-Da Hong1. 1. Biomedical Engineering Program, Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology; 2. Department of Physiology and Biophysics, National Defense Medical Center; 3. Division of Cardiology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center; 4. Department of Biomedical Engineering and Institute of Physiology, National Defense Medical Center, Taipei, Taiwan.
Abstract
BACKGROUND: It has been observed that acetaminophen shows cardioprotective efficacy in mammals. In this study, we investigated the electromechanical effects of acetaminophen on the left atrium (LA). METHODS: Conventional microelectrodes were used to record the action potentials (AP) in rabbit LA preparations. The action potential duration (APD) at repolarization levels of 90%, 50% and 20% of the AP amplitude (APD90, APD50, and APD20, respectively), resting membrane potential, and contractile force were measured during 2 Hz electrical stimulation before and after sequential acetaminophen administration to the LA. RESULTS: Acetaminophen (0.1, 0.3, 1, and 3 mM) reduced APD20 from 9.4 ± 1.2 to 8.0 ± 1.1 (p < 0.05), 7.1 ± 0.8 (p < 0.05), 7.8 ± 1.1, and 6.8 ± 1.2 ms (p < 0.05), respectively, and APD50 from 20.2 ± 1.9 to 17.4 ± 2.0, 15.6 ± 1.8 (p < 0.05), 15.8 ± 2.2 (p < 0.05), and 14.1 ± 2.4 ms (p < 0.05), respectively, in a concentration-dependent manner. APD90 was reduced from 72.0 ± 3.6 to 64.7 ± 4.2, 61.9 ± 4.3, 60.5 ± 3.7, and 53.4 ± 4.4 ms (p < 0.05), respectively. Acetaminophen increased LA contractility from 45 ± 9 to 52 ± 10 (p < 0.05), 55 ± 9 (p < 0.01), 58 ± 9 (p < 0.01), and 60 ± 9 mg (p < 0.01), respectively, in a concentration-dependent manner. In the presence of the NOS inhibitor L-NAME or PKG-I inhibitor DT-2, additional acetaminophen treatment did not significantly increase LA contractility. CONCLUSIONS: Acetaminophen modulated the electromechanical characteristics of LA by inhibiting the NOS and PKG I pathway, and then contributed to the positive inotropic effect.
BACKGROUND: It has been observed that acetaminophen shows cardioprotective efficacy in mammals. In this study, we investigated the electromechanical effects of acetaminophen on the left atrium (LA). METHODS: Conventional microelectrodes were used to record the action potentials (AP) in rabbit LA preparations. The action potential duration (APD) at repolarization levels of 90%, 50% and 20% of the AP amplitude (APD90, APD50, and APD20, respectively), resting membrane potential, and contractile force were measured during 2 Hz electrical stimulation before and after sequential acetaminophen administration to the LA. RESULTS:Acetaminophen (0.1, 0.3, 1, and 3 mM) reduced APD20 from 9.4 ± 1.2 to 8.0 ± 1.1 (p < 0.05), 7.1 ± 0.8 (p < 0.05), 7.8 ± 1.1, and 6.8 ± 1.2 ms (p < 0.05), respectively, and APD50 from 20.2 ± 1.9 to 17.4 ± 2.0, 15.6 ± 1.8 (p < 0.05), 15.8 ± 2.2 (p < 0.05), and 14.1 ± 2.4 ms (p < 0.05), respectively, in a concentration-dependent manner. APD90 was reduced from 72.0 ± 3.6 to 64.7 ± 4.2, 61.9 ± 4.3, 60.5 ± 3.7, and 53.4 ± 4.4 ms (p < 0.05), respectively. Acetaminophen increased LA contractility from 45 ± 9 to 52 ± 10 (p < 0.05), 55 ± 9 (p < 0.01), 58 ± 9 (p < 0.01), and 60 ± 9 mg (p < 0.01), respectively, in a concentration-dependent manner. In the presence of the NOS inhibitor L-NAME or PKG-I inhibitor DT-2, additional acetaminophen treatment did not significantly increase LA contractility. CONCLUSIONS:Acetaminophen modulated the electromechanical characteristics of LA by inhibiting the NOS and PKG I pathway, and then contributed to the positive inotropic effect.
Entities:
Keywords:
Acetaminophen; Contractility; Left atrium
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