Temperature and the relative contributions of ca transport systems
in cardiac myocyte relaxation.
Puglisi, Jos[acute]e L., Rosana A. Bassani, Jos[acute]e W. M. Bassani,
Jatin N. Amin, and Donald M. Bers.
Department of Physiology, Loyola University School of Medicine,
Maywood, IL 60153, USA
APStracts 2:0468H, 1995.
The relative contributions of the different Ca transport systems
involved in cardiac relaxation were evaluated at 25 degrees C and 35
degrees C in isolated rabbit, ferret and cat ventricular myocytes
during twitches (Tw), caffeine-induced contractures in normal Tyrode
solution (NTCaff) and caffeine-induced contractures in 0Na,0Ca
solution (Caff00). The time course of intracellular [Ca] ([Ca]i)
decline during these contractions in rabbit ventricular myocytes
allowed estimates of the relative contributions of the sarcoplasmic
reticulum (SR) Ca-pump, Na/Ca exchange (Na/CaX), sarcolemmal Ca-pump
and the mitochondrial calcium uniporter (with the latter two
considered together as "Slow Mechanisms"). The percent
contributions of the SR:NaCaX:Slow Mechanisms were 70:27:3 at 25
degrees C and 74:23:3 at 35 degrees C. Warming from 25 degrees to 35
degrees C decreases twitch contractions in rabbit and ferret
myocytes, and NTCaff and Caff00 contractures in all species. In
contrast, in cat myocytes warming increased twitches, possibly due to
a stronger effect of temperature on Ca influx. We conclude that
increased temperature accelerates all of the Ca transport systems
involved in relaxation. Despite large changes in each Ca transport
system with warming, the relative contributions during relaxation
remain similar at physiological temperature.
Received 19 June 1995; accepted in final form 29 September 1995.
APS Manuscript Number H559-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95