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|Title:||The role of pacing rate in the modulation of mechano-induced immediate and delayed changes in the force and Ca-transient of cardiac muscle|
|Citation:||Lookin O. The role of pacing rate in the modulation of mechano-induced immediate and delayed changes in the force and Ca-transient of cardiac muscle / O. Lookin, X. Butova, Y. Protsenko. — DOI 10.1016/j.pbiomolbio.2020.05.005 // Progress in Biophysics and Molecular Biology. — 2021. — Vol. 159. — P. 34-45.|
|Abstract:||Myocardial function is tuned by dynamic changes in length and load via mechano-calcium feedback. This regulation may be significantly affected by heart rhythm. We evaluated the mechano-induced modulation of contractility and Ca-transient (CaT) in the rat myocardium subjected to twitch-by-twitch shortening–re-lengthening (↓–↑) trains of different lengths (N = 1 … 720 cycles) at low (1 Hz) and near-physiological (3.5 Hz) pacing rates. Force/CaT characteristics were evaluated in the first post-train isometric twitch (immediate effect) and during slow changes (delayed maximal elevation/decrease) and compared with those of the pre-train twitch. The immediate inotropic effect was positive for N = 30 … 720 and negative for N = 1 … 20, while the delayed effect was always positive. The immediate and delayed inotropic effects were significantly higher at 3.5-Hz vs 1-Hz (P < 0.05). The prominent inotropism was accompanied by much smaller changes in the CaT diastolic level/amplitude. The shortening–re-lengthening train induced oscillations of the slow change in force at 3.5-Hz (always) and at 1-Hz (∼50% of muscles), which were dependent of the train length and independent of the pacing rate. We suggest that twitch-by-twitch shortening–re-lengthening of cardiac muscle decreases Ca2+ buffering by troponin C and elevates Ca2+ loading of the sarcoplasmic reticulum (SR); the latter cumulatively depends on the train length. A high pacing rate intensifies the cumulative transient shift in the SR Ca2+ loading, augmenting the post-train inotropic response and prolonging its recovery to the pre-train level. The pacing-dependent mechano-induced inotropic effects remain to be elucidated in the myocardium with impaired Ca handling. © 2020 Elsevier Ltd|
|Keywords:||(INTRA)CELLULAR CALCIUM BALANCE|
|metadata.dc.description.sponsorship:||The study was supported by RFBR grant # 18-04-00572 and by RF Government Act #211 of March 16, 2013 (agreement 02.A03.21.0006 ), and was carried out within the framework of the IIF UrB RAS theme No АААА-А18-118020590031-8 .|
|Appears in Collections:||Научные публикации, проиндексированные в SCOPUS и WoS CC|
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