CARDIAC MYOFILAMENT PROTEIN FUNCTION IS ALTERED DURING SEPSIS

Male Sprague-Dawley rats (350-500 g) were made septic by intraperitone al injection of 200 mg/kg cecal material in 5% dextrose in water (D5W; 5 ml/kg). Control rats (n=11) received D5W. Preparations were studied on days 1 (n=7), 3 (n=7), and 7 (n=8) of sepsis. In isolated hearts, ventricular function was depressed on days 3 and 7 of sepsis. Densitom etric analysis of myofilament proteins from Septic rats separated by S DS-PAGE showed no differences in relative amounts of actin, troponin, tropomyosin and myosin light chains compared to control. Myofilament f unction, assessed by measuring ATPase activities, was altered during s epsis. CA(2+)-independent Mg-ATPase activity was elevated on days 1 an d 3 of sepsis, returning toward control by day 7. Maximal ATPase activ ity was unchanged on day 1, but was increased on days 3 and 7 of sepsi s. Myofibrillar myosin K(EDTA)-, Ca2+-, and Mg2+-ATPase activities wer e not altered, nor were there any apparent changes in myosin heavy cha in isoform populations. Our data are the first to demonstrate alterati ons in minimal and maximal ATPase activities and myofilament CA(2+)-se nsitivity during chronic peritoneal sepsis. These alterations may cont ribute to observed changes in ventricular function. (C) 1998 Academic Press Limited.