Effects of Heart Rate on the Pump Function and Electrophysiological Characteristics of the Heart in the Frog Rana temporaria
¹Institute of Physiology, Komi Science Center, Urals Branch of the RAS, ²Syktyvkar State University named after Pitirim Sorokin; Syktyvkar, Komi Republic, the Russian Federation
*Corresponding author: Natalya A. Kibler, PhD; Laboratory of Cardiac Physiology, Institute of Physiology, Komi Science Center, Urals Branch of the RAS,Syktyvkar, Komi Republic, Russia. E-mail address: firstname.lastname@example.org
Published: March 17, 2017. doi: 10.21103/Article7(1)_OA5
The aim of the study was to investigate the electrical activity and contractility of the heart ventricle in frogs Rana temporaria (n=14) under different heart rates. The activation time (AT, as dV/dtmin during QRS complex), the repolarization time (RT, as dV/dtmax during ST-T wave), and the activation-recovery intervals (ARIs, as difference between RT and AT) were measured. The hemodynamic variables were determined with the Prucka MacLab 2000 system. Heart rate (HR) was changed by the use of right atrium pacing from 0.6 to 1.1Hz with step 0.1Hz. The increasing HR from 0.6 Hz to 1.1Hz led to the increased duration of ARIs on the ventral and dorsal fragments of ventricular epicardium as compared with initial sinus rhythm. During the high HR, more prolonged ARIs were observed on the ventral side of the epicardium than on the dorsal surface (exclusion is supraventricular rhythm with rate of 1.1Hz). The repolarization dispersion of epicardium on the whole, as well as repolarization of both epicardial sides separately, decreased under the higher rate. Repolarization sequence depended on the activation sequence and the distribution of local repolarization durations only at supraventricular rhythm with a frequency of 1.1Hz. The indexes of pump function decreased under high HR.
Thus, the increased HR resulted in a decrease in the dispersion of repolarization and ARIs; the repolarization duration of ventricular epicardium at supraventricular rhythms was shortened as compared with sinus rhythm. During an increase in HR, repolarization sequence is formed in association with the level of ARI dispersion and changes of the repolarization duration.
1. Jensen J, Wang T, Christoffels VM, Moorman AF. Evolution and development of the building plan of the vertebrate heart. Biochim Biophys Acta. 2013;1833(4):783-94.
2. Lillywhite HB, Zippel KC, Farrell AP. Resting and maximal heart rates in ectothermic vertebrates. Comp Biochem Physiol A Mol Integr Physiol. 1999;124(4):369-82.
3. Davies F, Francis ET. The conducting system of the vertebrate heart. Biol Rev Camb Phylos Soc. 1946;21(4):173-88.
4. Moorman AF, Christoffels VM. Cardiac chamber formation: development, genes, and evolution. Physiol Rev. 2003; 83(4):1223-67.
5. Sedmera D, Reckova M, deAlmeida A, Sedmerova M, Biermann M, Volejnik J, et al. Functional and morphological evidence for a ventricular conduction system in zebrafish and Xenopus hearts. Am J Physiol Heart Circ Physiol. 2003;284(4):H1152-60.
6. Berger RD, Wolff MR, Anderson JH, Kass DA. Role of atrial contraction in diastolic pressure elevation induced by rapid pacing of hypertrophied canine ventricle. Circ Res. 1995; 77(1):163-73.
7. de Pauw M, Vilaine JP, Heyndrickx GR. Role of force-frequency relation during AV-block, sinus node block and beta-adrenoceptor block in conscious animals. Basic Res Cardiol. 2004; 99 (5):360-71.
8. Vogel M, Cheung MM, Li J, Kristiansen SB, Schmidt MR, White PA, Sorensen K, et al. Noninvasive assessment of left ventricular force-frequency relationships using tissue Doppler-derived isovolumic acceleration: validation in an animal model. Circulation. 2003; 107(12):1647-52.
9. Weidermann F, Fadi J, Sutherland GR, Claus P, Kowalski M, Hatle L, et al. Myocardial function defined by strain rate and strain during alterations in inotropic states and heart rate. Am J Physiol Heart Circ Physiol. 2002;283(2):792-9.
10. Bowditch HP. Does the Apex of the Heart contract automatically? J Physiol. 1878; 1(1):104–7.
11. Carey C. Factors affecting body temperatures of toads. Oecologia. 1978; 35:197-219.
12. Branco LG, Wood SC. Effect of temperature on central chemical control of ventilation in the alligator Alligator mississippiensis. J Exp Biol. 1993;179:261-72.
13. Chapovetsky V, Katz U. Effects of season and temperature acclimation on electrocardiogram and heart rate of toads. Comp Biochem Physiol A Mol Integr Physiol. 2003; 134(1):77-83.
14. Mazza R, Pasqua T, Cerra MC, Angelone T, Gattuso A. Akt/eNOS signaling and PLN S-sulfhydration are involved in H2S-dependent cardiac effects in frog and rat. Am J Physiol Regul Integr Comp Physiol. 2013;305(4):443-51.
15. Millar CK, Kralios FA, Lux RL. Correlation between refractory periods and activation-recovery intervals from electrograms: effects of rate and adrenergic interventions. Circulation. 1985;72(6):1372-9.
16. Lagerspetz K. Interaction of season and temperatureacclimation in the control of metabolism in amphibian. Thermal Biol. 1977; 2:223-31.
17. Katz U, Hoffman J, Gil N. What is the ecological significance of laboratory temperature selection in anuran Amphybia? Alytes. 1997;15:91-8.
18. Shemarova IV, Kuznetsov SV, Demina IN, Nesterov VP. T-channels and Na+,Ca2+-exchangers as components of the Ca2+-system of the myocardial activity regulation of the frog Rana temporaria. Zh Evol Biokhim Fiziol. 2009;45(3):319-28. [Article in Russian].
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International Journal of Biomedicine. 2017;7(1):46-50. © 2017 International Medical Research and Development Corporation. All rights reserved.