Ca2+ uptake by cardiac sarcoplasmic reticulum at low temperature in
rat and ground squirrel.
Liu, Bin, Darrell D. Belke, and Lawrence C. H. Wang.
Depts. of Pharmacology and Biological Sciences, University of
Alberta, Edmonton, T6G 2E9 Alberta, Canada
APStracts 3:0310R, 1996.
The Ca2+ uptake by isolated cardiac sarcoplasmic reticulum (SR) was
compared between Richardson's ground squirrels and rats at 37, 25,
15, and 5oC. The rate of SR Ca2+ uptake in ground squirrels was
significantly higher than in rats over the temperature range. This
marked species difference was observed over a [Ca2+] range from 0.1
to 10 [mu]M. The Arrhenius plot for Ca2+ uptake was linear for ground
squirrels between 37 and 5oC but showed a depression from linearity
for rats at 5oC. This temperature sensitivity was also reflected in
rat SR Ca2+-ATPase activity. Analysis of 3H-ryanodine binding in SR
suggests that more Ca2+ release channels are in an open state at low
temperatures in rats than in ground squirrels. Together, these
results suggest that species differences in the response of SR to low
temperature may account for the rise in [Ca2+]i in cold-sensitive
species, and may be responsible, at least in part, for the inability
of cold-sensitive hearts to function at low temperature.
Received 27 February 1996; accepted in final form 22 July 1996.
APS Manuscript Number R116-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996