HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 100/5/1727    most recent 01244.2005v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Hiranandani, N. Articles by Janssen, P. M. L. Search for Related Content PubMed PubMed Citation Articles by Hiranandani, N. Articles by Janssen, P. M. L.

HIGHLIGHTED TOPICS
A Physiological Systems Approach to Human and Mammalian Thermoregulation

Frequency-dependent contractile response of isolated cardiac trabeculae under hypo-, normo-, and hyperthermic conditions

Department of Physiology and Cell Biology, The Ohio State University, Columbus, Ohio

Submitted 29 September 2005 ; accepted in final form 30 December 2005

The body is from time to time exposed to nonnormothermic conditions; both hypo- and hyperthermia can occur as a result of external (environment) or internal (pathogens, allergens) stressors. To preserve life under hypo- and hyperthermic conditions, adequate perfusion of vital organs is mandated. Although cardiac output regulation under hyperthermic conditions has been studied, the mechanical response of basic contractile function of the myocardium itself is incompletely understood. Accordingly, we set out to test mechanical output of isolated myocardium under hyperthermic conditions and to compare the results with the hypo- and normothermic response in the same tissue. We observed that, in absence of a frequency change, developed force decreased markedly. At a physiological normal stimulation rate of 6 Hz, developed force decreases to 67.2 ± 2.6% at 42°C compared with 37°C. In addition, twitch timing characteristics also accelerate, allowing for a faster relaxation; time from peak tension to 50% relaxation is 23% faster (from 31.4 ± 2.6 to 24.4 ± 1.7 ms). Although this faster relaxation in turn prevents a steep increase in diastolic tension at high frequencies, the very fast calcium kinetics now prevent a more complete activation of the myofilaments, resulting in a lower twitch-force maximum at hyperthermic conditions. Even at maximal -adrenergic stimulation, developed force is well below levels reached at physiological temperature.

fever; force-frequency relationship; beta-adrenergic stimulation; isoproterenol; thermoregulation

This article has been cited by other articles:

				O. Cohen, H. Kanana, R. Zoizner, C. Gross, U. Meiri, M. D. Stern, G. Gerstenblith, and M. Horowitz Altered Ca2+ handling and myofilament desensitization underlie cardiomyocyte performance in normothermic and hyperthermic heat-acclimated rat hearts J Appl Physiol, July 1, 2007; 103(1): 266 - 275. [Abstract] [Full Text] [PDF]