Myothermal economy of rat myocardium, Chronic adaptation versus acute inotropism
By means of rapid planar Hill type antimony-bismuth thermopiles the initial heat liberated by papillary muscles was measured synchronously with developed tension for control (C), pressure-overload (GOP), and hypothyrotic (PTU) rat myocardium (chronic experiments) and after application of 10−6 M isoproterenol or 200 10−6 M UDCG-115. Economy of force production was analyzed by the ratio of initial heat versus developed tension-time integral. This ratio was found to be reduced by 34% in GOP and by 43% in PTU myocardium (P <0.01, respectively) indicating increased economy of force production. In contrast, isoproterenol increased initial heat versus tension-time integral by 70% (P<0.01) indicating reduced economy of force production. No change in this ratio was found for UDCG-115. The presented data indicates that long and short term modulation of myocardial energetic costs of force generation is possible. The basic mechanisms for these myocardial alterations are discussed.
Key wordsmyothermal economy pressure overload hypothyroidism catecholamines positive inotropic drugs initial heat
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- 2.Alpert NR, Mulieri LA (1982) The functional significance of altered tension dependent heat in thyrotoxic myocardial hypertrophy. Basic Res Cardiol 75: 153–159Google Scholar
- 5.Blanchard EM, Mulieri LA, Alpert NR (1984) The effect of 2,3-Butenedione monoxime (BDM) on the relation between initial heat and mechanical output and on the activity of the contractile apparatus of rat papillary muscle. Conference of Muscle Energetics, Burlington, VermontGoogle Scholar
- 9.Gibbs CL (1967) Role of catecholamines in heat production in the myocardium. Circ Res 21 (Suppl III): 223–230Google Scholar
- 15.Holubarsch Ch, Goulette RP, Mulieri LA, Alpert NR (1983) Heat liberation in experimentally induced tetanic contractions of myocardium from normal and Goldblatt rats. In: Jacob R (ed) Cardiac Adaptation of Hemodynamic Overload, Training and Stress. Steinkopff Verlag, Darmstadt, pp 158–166CrossRefGoogle Scholar
- 17.Kretzschmar KMM, Wilkie DR (1972) A new method for absolute heat measurements, utilizing the Peltier effect. J Physiol (Lond) 224: 18p - 20 pGoogle Scholar
- 21.Mulieri LA, Luhr G, Trefry J, Alpert NR (1977) Metal-film thermopiles for use with rabbit right ventricular papillary muscles. Am J Physiol 233: C 136 - C156Google Scholar
- 22.Rüegg JC, Pfitzer G (1984) Myokardkontraktilität and Phosphorylierung der kontraktilen Proteine. In: Keul J, H-H Dickhuth (eds) Herzinsuffizienz. Pathophysiologie, Klinik and Therapie. Perimed Fachbuch-Verlagsgesellschaft, Erlangen, pp 53–56Google Scholar