Heat production during hypoxic contracture of rat myocardium.
- 1 December 1982
- journal article
- research article
- Published by Wolters Kluwer Health in Circulation Research
- Vol. 51 (6) , 777-786
- https://doi.org/10.1161/01.res.51.6.777
Abstract
Contracture due to hypoxia, to both oxygen and glucose deficiency, and to potassium chloride was induced in rat left ventricular papillary muscle preparations. Under contracture conditions, the sum of resting heat plus contracture heat was measured using Hill-type, planar vacuum-deposited thermopiles. On the basis of the measured total and initial heat output and the corresponding tension-time integral during single twitches under control conditions (Lmax, 21 degrees C, stimulus frequency 12/min), the expected heat output during contracture was calculated, assuming that the contracture tension is maintained by the same calcium-induced cross-bridge cycling as occurs in the single twitch response. With potassium chloride, the contracture tension was 1.33 +/- 0.27 g/mm2, a value which is similar to those found in hypoxic contracture and in contracture due to both oxygen and glucose deficiency. There was no significant difference between measured and calculated values for resting heat plus contracture heat (8.40 +/- 2.84 mW/g measured, 8.55 +/- 2.50 mW/g calculated); there was a linear correlation (r = 0.99) between predicted and measured values (P less than 0.05). The measured value for resting plus contracture heat in hypoxic contracture was 1.88 +/- 0.37 mW/g, whereas a value of 4.80 +/- 1.09 mW/g (P less than 0.005) was calculated on the basis of the twitch heat per tension-time integral and contracture tension (1.09 +/- 0.31 g/mm2). Contracture tension was 1.80 +/- 0.78 g/mm2 in contracture due to oxygen and glucose deficiency, whereas the value for resting plus contracture eat was 1.61 +/- 0.56 mW/g. The calculated resting plus contracture heat value for this preparation was significantly higher (7.45 +/- 3.75 mW/g; P less than 0.05). There was no significant regression between predicted and measured resting heat plus contracture heat in the hypoxic contracture preparations (slope not different from zero). In contracture due to oxygen and glucose deficiency, the linear regression had a slope of 6.06 (P less than 0.05). The results suggest that the potassium chloride contracture relies on cross-bridge cycling as in a twitch contraction, whereas hypoxic contracture and that due to oxygen and glucose deficiency may be explained by cross-bridge formations with no, or very low, heat production, i.e., contracture tensions due to hypoxia and to oxygen and glucose deficiency are maintained by rigor-like cross-bridge formation or by slowly cycling cross-bridges with a long time of cross-bridge attachment.This publication has 37 references indexed in Scilit:
- Modulation of tension generation at the myofibrillar level—an analysis of the effect of magnesium adenosine triphosphate, magnesium, pH, sarcomere length and state of phosphorylationBasic Research in Cardiology, 1980
- Contracture type and fibrosis type of decreased myocardial distensibility. Different changes in elasticity of myocardium in hypoxia and hypertrophyBasic Research in Cardiology, 1980
- The functional significance of altered tension dependent heat in thyrotoxic myocardial hypertrophyBasic Research in Cardiology, 1980
- The effect of calcium and high-energy phosphate compounds on myocardial contracture in the newborn and adult rabbitJournal of Molecular and Cellular Cardiology, 1978
- Ischemic contracture of the myocardium: Mechanisms and preventionThe American Journal of Cardiology, 1977
- The partitioning of altered mechanics in hypertrophied heart muscle between the sarcoplasmic reticulum and the contractile apparatus by means of myothermal measurementsBasic Research in Cardiology, 1977
- Further observations on species-determined differences in the calcium-accumulating activity of cardiac microsomal fractionsJournal of Molecular and Cellular Cardiology, 1975
- Changes in Diastolic Stiffness and Tone of the Left Ventricle During Angina PectorisCirculation, 1974
- Contracture and Catecholamines in Mammalian MyocardiumScience, 1969
- Recovery heat in muscleProceedings of the Royal Society of London. B. Biological Sciences, 1939