| Effect of Twitch Interval Duration on the Contractile Function of Subsequent Twitches in Isolated Rat, Rabbit, and Dog Myocardium under Physiological Conditions. | |
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MedLine Citation:
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PMID: 21778421 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Many studies have shown that a change in stimulation frequency leads to altered contractility of the myocardium. However, it remains unclear what changes occur directly after a change in frequency, and which ones are a result of the slow processes that lead to the altered homeostasis that develops after a change in stimulation frequency. To distinguish the immediate from the slow responses, we assessed contractile function in two species that have distinctively different calcium handling properties using a recently developed randomized pacing protocol. In isolated dog and rat right ventricular trabeculae, twitch contractions at 5 different cycle lengths within the physiologic range of each species were randomized around a steady state frequency. We found, in both species, that the duration of the cycle length just prior to the analyzed twitch (primary) positively correlated with the increased force of the analyzed twitch. In sharp contrast, the cycle lengths one and two more removed from the analyzed twitch ("secondary" and "tertiary") displayed a negative correlation with force of the analyzed twitch. In additional experiments, assessment of intracellular calcium transients in rabbit trabeculae revealed that diastolic calcium levels were closely correlated to contractile function outcome. The relative contribution of the primary cycle length was different between dog (51%) and rat (71%), while in neither species a significant effect on relaxation times was observed. Using randomized cycle lengths, we have distinguished the intrinsic response from the signaling-mediated effects of frequency-dependent activation on myofilament properties and calcium handling. |
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Authors:
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Ying Xu; Michelle M Monasky; Nitisha Hiranandani; Kaylan M Haizlip; George E Billman; Paul M L Janssen |
Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-7-21 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: - ISSN: 1522-1601 ISO Abbreviation: - Publication Date: 2011 Jul |
Date Detail:
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Created Date: 2011-7-22 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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1The Ohio State University. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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