Temperature-dependent postextrasystolic potentiation and Ca(2+) recirculation fraction in canine hearts.
We have found that cardiac temperature proportionally changes O(2) cost of contractility, defined as O(2) consumption for myocardial total Ca(2+) handling normalized to contractility in terms of the end-systolic pressure-volume ratio (maximal elastance, E(max)), in the canine left ventricle (temperature sensitivity, Q(10) = 2). We have separately found that a decrease in the recirculation fraction (RF) of Ca(2+) within myocardial cells underlies an increased O(2) cost of E(max) in stunned hearts. We therefore hypothesized that a similar change in RF would underlie the Q(10) of O(2) cost of E(max). We tested this hypothesis by analyzing RF calculated from an exponential decay component of the transiently alternating postextrasystolic potentiation in the canine left ventricle. RF decreased from 0.7 to 0.5 as cardiac temperature increased from 33 to 38 degrees C with Q(10) of 0.5, reciprocal to that of O(2) cost of E(max). We conclude that Q(10) of ATP-consuming reactions involved in Ca(2+) handling and E(max) response to it could reasonably account for the reciprocal Q(10) of RF and O(2) cost of E(max).
Mizuno
Ju
J
Department of Cardiovascular Physiology, Okayama University Graduate School of Medicine and Dentistry, Okayama, 700-8558, Japan.
Araki
Junichi
J
Suzuki
Shunsuke
S
Mohri
Satoshi
S
Mikane
Takeshi
T
Shimizu
Juichiro
J
Matsubara
Hiromi
H
Hirakawa
Masahisa
M
Ohe
Tohru
T
Suga
Hiroyuki
H
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001831:Body Temperature / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D003198:Computer Simulation; D004285:Dogs; D006329:Heart Conduction System / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D008955:Models, Cardiovascular; D009200:Myocardial Contraction / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D016277:Ventricular Function, Left / Q000502:physiology; D018879:Ventricular Premature Complexes / Q000503:physiopathology*
D000255:Adenosine Triphosphate; D010100:Oxygen; D002118:Calcium