AJP - Cell Physiology, Vol 258, Issue 2 C274-C281, Copyright © 1990 by American Physiological Society
Temperature dependence of myofilament Ca sensitivity of rat, guinea pig, and frog ventricular muscle
S. M. Harrison and D. M. Bers
Division of Biomedical Sciences, University of California, Riverside 92521.
Cooling the superfusate of intact ventricular muscle, from 30 degrees C to
below 4 degrees C in less than 2 s, leads to contractures thought to
reflect the amount of Ca available for release from the sarcoplasmic
reticulum (SR). On rewarming, tension transiently increases in guinea pig
and rat ventricular muscle. It has been proposed that this rewarming
tension spike reflects changes in myofilament Ca sensitivity and maximum
Ca-activated force (Cmax) associated with rewarming. There are differences
in intracellular Ca regulation among cardiac muscle preparations. Some
characteristics of rapid-cooling contractures (e.g., the magnitude of the
rewarming spike) also differ between species. Therefore, the Ca sensitivity
of skinned ventricular muscle from the rat, guinea pig, and frog was
determined at 29 (22 degrees C for frog ventricular preparations), 8, and 1
degrees C. The results show that cooling rat and guinea pig ventricular
muscle from 29 to 1 degrees C shifts the pCa vs. tension relationship
toward higher [Ca2+] by 0.65 and 0.55 pCa units, respectively. Cooling to 1
degrees C also reduced Cmax to 3.3 and 7.8% of that at 29 degrees C in rat
and guinea pig ventricular muscle, respectively. Similar results were found
for frog ventricular muscle, in which cooling from 22 to 1 degrees C
reduced Ca sensitivity by 0.6 pCa units and Cmax to 45.7% of its value at
22 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)
