Energetic aspects of inotropic interventions in XXXX myocardium.

@entity35 @entity15480 @entity460 @entity3044 @entity734
Contractile force of the myocardium can be increased by different molecular mechanisms, and therefore different energetic consequences may result. The influence of the inotropic substances @entity3044 and UDCG-115 on myocardial energetics in isometrically contracting left ventricular @entity35 papillary muscles was investigated by means of highly sensitive antimony bismuth thermopiles. @entity3044 increased total heat and initial heat by 147% (p less than 0.01) and 69% (p less than 0.02) when normalized to tension-time integral, respectively. No significant change of both heat terms occurred due to UDCG-115. Initial heat was separated into tension-independent heat (" @entity460 cycling") and @entity734 ("cross-bridge cycling") by means of a new method using @entity15480 . Both @entity734 per tension-time integral and tension-independent heat increased significantly, due to @entity3044 , from 4.9 +/- 1.17 to 7.6 +/- 2.72 mu cal/g.cm.s (p less than 0.05) and from 0.15 +/- 0.06 to 0.22 +/- 0.04 mcal/g (p less than 0.01). UDCG-115 influenced neither tension-independent heat nor @entity734 per tension-time integral significantly. Thus, the economy of force development was not significantly altered due to UDCG-115 whereas @entity3044 significantly increased the energy necessary for activation, i.e. @entity460 cycling, and the energy necessary for force production, i.e. cross-bridge cycling. The basic mechanisms of these energetic changes are discussed.
