EFFECTS OF ESCHERICHIA-COLI SEPSIS AND MYOCARDIAL DEPRESSANT FACTOR ON INTERVAL-FORCE RELATIONS IN DOG VENTRICLE

We examined whether depressed left ventricular (LV) contractility duri ng Escherichia coli sepsis in dogs was due to a decrease in the fracti onal release of calcium from the sarcoplasmic reticulum (SR) or a redu ction in calcium content in this organelle. To indirectly assess SR ca lcium availability in a right ventricular (RV) trabecular muscle prepa ration, we utilized functional indexes of cellular myocardial calcium metabolism, which included rapid-cooling contracture (RCC), an indicat or of SR calcium content, and postrest contraction (PRC), an index of calcium availability from the release compartment of the SR. Measureme nts were made during steady-state stimulation at 0.5 and 1.5 Hz, durin g which time rest intervals of 30-240 s were periodically imposed. SR calcium availability was measured in RV trabeculae of dogs subjected t o 4 h of E. coli sepsis and was compared with calcium availability mea sured in nonseptic dogs. We further characterized a filterable cardiod epressant substance (FCS), which has been previously shown to be assoc iated with LV depression in this model, to determine whether it produc ed changes in calcium metabolism similar to those found in sepsis. The results showed that calcium availability from the SR of septic dogs w as not impaired. Furthermore, FCS was found in the 10,000- to 30,000-m ol wt fraction of plasma and produced changes in PRC in canine trabecu lae that were similar to those produced during sepsis. We conclude tha t, as assessed by PRC and RCC, SR calcium content and release are not impaired in sepsis.