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Contraction of atrial smooth muscle reduces cardiac output in perfused turtle hearts

Journal article
Authors W. Joyce
Michael Axelsson
T. Wang
Published in Journal of Experimental Biology
Volume 222
Issue 6
ISSN 0022-0949
Publication year 2019
Published at Department of Biological and Environmental Sciences
Language en
Keywords Stroke volume, Diving, Cardiac filling, Tonus waves, tonus waves, atrioventricular connection, intrinsic-properties, terrapin, anoxia, drugs, catecholamines, autoregulation, 5-degrees-c, performance, Life Sciences & Biomedicine - Other Topics
Subject categories Biological Sciences


Unusual undulations in resting tension (tonus waves) were described in isolated atria from freshwater turtles more than a century ago. These tonus waves were soon after married with the histological demonstration of a rich layer of smooth muscle on the lumina) side of the atrial wall. Research thereafter waned and the functional significance of this smooth muscle has remained obscure. Here, we provide evidence that contraction of the smooth muscle in the atria may be able to change cardiac output in turtle hearts. In in situ perfused hearts of the red-eared slider turtle (Trachemys scripta elegans), we demonstrated that activation of smooth muscle contraction with histamine (100 nmol kg (-1) bolus injected into perfusate) reduced cardiac output by decreasing stroke volume (>50% decrease in both parameters). Conversely, inhibition of smooth muscle contraction with wortmannin (10 mu mol l(-1) perfusion) approximately doubled baseline stroke volume and cardiac output. We suggest that atrial smooth muscle provides a unique mechanism to control cardiac filling that could be involved in the regulation of stroke volume during diving.

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