Ischemia of the heart : a study of sarcomere dynamics and cellular metabolism

The following hypotheses were tested: 1. The properties of the cardiac myoflorils, including the length dependence of calcium sensitivity, largely account for the shape of the ascending limb of the force - sarcomere length relation, both in intact and skinned cardiac muscle (Chapter 4). 2. Acidosis causes a shift of the force - pCa2+ curve to the right at all sarcomere lengths as a result of competition between H+ and Ca2+ ions for binding to the myofilaments (Chapter 5). 3. Strontium is able to induce maximal force development by direct activation of the contractile apparatus and stimulation of calcium release by the sarcoplasmic reticulum (Chapter 6). 4. During hypoxic perfusion followed by flow standstil, rat cardiac muscle develops rigor in spite of the fact that concentrations of high-energy phosphates are only slightly diminished (Chapte' 7). 5. The increased diastolic force that is observed during hypoxia of rat heart can nearly completely be explained on the basis of formation of rigor bonds (Chapter 8). 6. Impaired relaxation during repeated hypoxia is accounted for by calcium overload without evidence for rigor bound formation or a shift of the diastolic force - SL relation (Chapte' 9). These hypotheses will be addressed in more detail in the chapters that are mentioned in parentheses.