Myocardial oxygen consumption of mechanically unloaded contraction
of rat ventricular slices by a new approach.
Yasuhara, Shingo, Miyako Takaki, Akio Kikuta, Haruo Ito, and Hiroyuki
Suga.
Departments of Physiology II and Anatomy, Okayama University
Medical School, 2-5-1 Shikata-cho, Okayama, 700 Japan
APStracts 2:0398H, 1995.
We instituted a new approach of measuring mechanically unloaded
myocardial oxygen consumption (VO2) by using rat left ventricular
(LV) slices in an air-tight chamber filled with oxygenated Tyrode
solution. Myocardial slices (300 [mu]m in thickness) freely shortened
without external load by electrical field stimulation (St). VO2
without St was 1.69 +/- 0.41 (n = 6) ml O2 x min-1 x 100 g LV-1. VO2
with St increased to 2.28 +/- 0.36 (n = 6) ml O2 x min-1 x 100 g LV
-1. VO2 in calcium (Ca2+) free Tyrode solution irrespective of St was
nearly equal to the VO2 without St in normal Tyrode solution,
indicating all these VO2 to correspond to basal metabolic VO2. The
increment in VO2 by St (_VO2) increased up to twice normal with the
extracellular Ca2+ concentration up to 4 times normal. Inhibition of
crossbridge cycling by 2,3-butanedione monoxime (5 and 10 mM) did not
decrease _VO2. These results suggest that _VO2 consists of VO2
primarily for excitation-contraction (E-C) coupling but not for
crossbridge cycling.
Received 7 March 1995; accepted in final form 28 August 1995.
APS Manuscript Number H213-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.