Oxygen costs of left ventricular contractility for dobutamine and Ca(2+) in normal rat hearts and the cost for dobutamine in Ca(2+) overload-induced failing hearts.
The aim of the present study was to compare the oxygen (O(2)) cost of left ventricular (LV) contractility (equivalent maximal elastance; eEmax, an index for contractility) for dobutamine (a beta-receptor stimulant) with that for calcium (Ca(2+)) in normal rat hearts and to assess the O(2) cost of LV eEmax for dobutamine in Ca(2+) overload-induced failing rat hearts. The mean O(2) cost of LV eEmax (x10(-4) microl O(2) x beat(-1) x mmHg(-1) x ml x g(-2)) for Ca(2+) was 1.30+/-0.37 in 12 normal hearts, and for dobutamine it was 1.26+/-0.30 in eight different normal hearts. In the same five normal hearts, the mean O(2) cost of LV eEmax for dobutamine was 1.15+/-0.27, and for Ca(2+) it was 0.81+/-0.36. These mean values showed no significant differences between Ca(2+) and dobutamine. In five Ca(2+) overload-induced failing hearts, the mean O(2) cost of LV eEmax for Ca(2+) could not be assessed, but the mean O(2) cost of LV eEmax for dobutamine was 1.04+/-0.40. This mean value for dobutamine did not differ significantly from those (see above 1.26+/-0.30 or 1.15+/-0.27) in the normal hearts. The present results indicate, in terms of the coupling of mechanical work and energetics of the heart, that the total Ca(2+) handling VO(2) in excitation-contraction coupling against unit LV contractility change for dobutamine in the contractile failing hearts does not differ from that in the normal hearts. This suggests that in the Ca(2+) overload-induced contractile failing hearts, there were no changes in the sensitivity of the contractile machinery for Ca(2+), in the Ca(2+)/ATP in the total Ca(2+) handling, and in the ATP/VO(2) in the mitochondria.
Department of Surgery III, Nara Medical University, Kashihara, 634-8521 Japan.
Nobuoki
N
Tabayashi
Takehisa
T
Abe
Shuichi
S
Kobayashi
Yoshiro
Y
Yoshikawa
Susumu
S
Sakata
Chikako
C
Takenaka
Hiromi
H
Misawa
Shigeki
S
Taniguchi
Miyako
M
Takaki
D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology*; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004280:Dobutamine / Q000494:pharmacology*; D006333:Heart Failure / Q000188:drug therapy / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects* / Q000502:physiology; D017682:Myocardial Stunning / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology; D009206:Myocardium / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D016277:Ventricular Function, Left
D002316:Cardiotonic Agents; D004280:Dobutamine; D002122:Calcium Chloride